If you are driving on Interstate 90 across the Cascades, there are several ways to approach Snoqualmie Falls:
+ Exit the interstate at exit 25, and take the Snoqualmie Parkway from the Interstate to Highway 202. Turn left at the end of the parkway onto highway 202. Just after crossing the bridge, start to look for the visitor's parking lot on the right side of the road.
+ Exit at Preston and take the Preston - Falls City Road to Falls City, then turn right onto highway 202. The main parking lot to the top of the falls will be on your left as you come around a nearly blind curve, after about two miles of driving.
+ exit at North Bend, follow signs for highway 202, and turn left in the middle of downtown North Bend. The parking lot will be on your right as you go by the falls, and this will be a huge advantage to you as the road is not easy to make a left turn off of due to heavy tourist traffic.
+ exit at the Jackson Mountain area and go straight through North Bend, connecting to highway 202 in North Bend.
To me, the Snoqualmie Parkway method (the first one listed above) seems to make the most sense, as it avoids the slower speeds and roundabout roads of the various other methods.
By Public Transit:
+ From 2nd and University in downtown Seattle (or the transit tunnel, depending on the time of day and what day of the week) take SoundTransit bus route 554, the Issaquah Highlands Express to the Issaquah Park and Ride. Transfer to King County Metro bus route # 209, Issaquah - North Bend. Get off at the Snoqualmie Falls Lodge bus stop.
You can do this trip on weekdays or on Saturdays, but route 209 has no service on Sundays. If you make this trip on Saturday, you have to be careful of your departure time from downtown Seattle on SoundTransit, as there is a two hour gap between the first uphill #209 and the second one.
If you have time and are interested, both bus routes serve downtown Issaquah and intersect there as well. This is important to remember during periods when route 209 isn't operating very frequently, but Sound Transit 554 is operating - if you need to wait a while, downtown Issaquah is a much more interesting place, and possible to get around by walking, than the tangle of busy wide streets that surround the Issaquah transit center.
+ If you wish to visit the railroad museum, downtown Snoqualmie, and/or North Bend, the bus stop for that is only several stops down the road, and a very short distance. It is located in the city of Snoqualmie itself, and therefore it is covered in a different city.
+ If you are coming from the University of Washington district, it may be better to take King County Metro route # 271 to the Issaquah Transit Center, but that route takes about 20 minutes longer than the SoundTransit express from downtown Seattle, as it is a local bus. However, it is faster than taking a long diversion to downtown if you are already in that area. However, be warned that not all 271 buses go all the way to Issaquah.
+ Bus route 214 is an express from downtown Seattle to Snoqualmie and North Bend. However, it is primarily aimed at commuter traffic and therefore only operates towards downtown Seattle during the days and away from downtown Seattle during the evenings. If you are staying the night somewhere it could be useful for you, however. You would either need to use bus route 209 to get to the falls or take the walkway from Snoqualmie to Snoqualmie Falls (see my Walking to Snoqualmie Falls tip).
The standard trip from downtown Seattle to Snoqualmie Falls costs $4.50 one way if you are paying by cash fare ($2.50 for your trip on SoundTransit and $2.00 for your trip on King County Metro) or $2.50 if you have an ORCA card. These prices increase if you are making part of the trip during peak commuting hours. If you make the trip entirely on King County Metro the trip costs $2.00 one way off-peak and $2.25 peak period, but King County Metro does not operate a downtown Seattle to Issaquah bus. Thus, you would have to take the University District route if you want to save $2.50 from the cost of taking the SoundTransit express.
While it is possible to take a bus (King County Metro route 209) or drive between Snoqualmie Falls and downtown Snoqualmie, the fact is that the bus route operates only very occasionally, and the parking at Snoqualmie Falls is very limited.
As I arrived at the falls on Sept 18, 2010 by bus, and found that many items were closed until 2013 (my visit a year before there wasn't time, unfortunately, and now I have to wait a few years), driving was not an option as there was no car available to drive anywhere. It was going to be another hour and a half before the next bus arrived. I walked around the lodge a little bit looking to see if there was some sort of connector trail. There didn't seem to be, but I noticed a lot of joggers going through the hotel parking lot along the highway, and I decided to investigate further.
Here is what I found out: The Snoqualmie Falls Lodge has a guest parking lot that leads along the highway towards Snoqualmie. You can walk through this area (as I had seen the joggers run through) and at the far east side of the lodge, the shoulder of the highway becomes much wider than in the area around the falls parking lot.
You still wind up walking beside the highway shoulder for about 500 feet (150 meters), but once you get to a bridge over the Snoqualmie River, there is a walkway beside the bridge. From here into downtown Snoqualmie, there is a paved walkway that is separated from the highway by a wide planted strip.
The total distance between the Snoqualmie Falls viewpoint and downtown Snoqualmie Falls is approximately 3/4 of a mile (1.3 km), with no elevation gain to speak of. The only part that is a little questionable is the area beside the wide shoulder of the highway, and that doesn't last very long at all.
Photo 1: This is the separated walkway along Highway 202 as it looks between Snoqualmie and Snoqualmie Parkway (essentially the bridge over the Snoqualmie River). There are really nice boardwalks over the top of the local streams, as seen here. The separation from traffic is really nice.
Photo 2: The separation from traffic is really nice after walking along Highway 202 in the area between the Snoqualmie Falls Lodge and the Snoquamie River Bridge, as this little concrete curb is the only thing separating you from busy traffic on this busy section of road, but thankfully it only lasts for a very short distance.
Photo 3: This shows the lack of highway shoulder right at the falls lodge. To the left of this photo, there is an employee parking lot for the lodge that allows people to get from the falls to the wide shoulder section that runs beside highway 202. If it were not for that parking lot, you would not be able to get from the falls to Snoqualmie itself.
Photo 4: Here is the walkway beside the Snoqualmie River Bridge that connects the trail on one side of the river to the other, allowing someone to walk from the falls into the city of Snoqualmie.
Photo 5: Here is the transition from the highway 202 shoulder to the Snoqualmie River Bridge.