The best way to get around the city, not only St. Gallen, but in Switzerland in general is by train and by bus. 'Cause if you get a car, you'll probably have problems to find parkings...and if you find them. You can be sure that they are expensive.
At the main station you can get some more information about it...depending on how long you are staying, you can by discount tickets with extra trips.
In the summer you could have a bike to get around...many cities rent them for free...you just have to give them your ID and they will give it back when you return the bike.
In St. Gallen Railway Station, you may notice another small station. There is a narrow Gauge railway station which belongs to the Appenzell Railway. This station brings you steeply up hill and then on to the Appenzell region. Visiting Appenzell Town isnt a long trip.
Also near the main station you may notice the Orange Tram which goes to Trogen on the outskirts of St. Gallen. Another lovely short trip. Both trips are free if you have a Swiss Pass.
There's two main ways to get to Sankt-Gallen :
By the road :
By car from Zurich, head east on N1 (also called E17).
By train :
St. Gallen is on the main train lines connecting Zurich with Munich. At least a dozen trains per day arrive from both directions. Trip time from Zurich is about 75 minutes. St. Gallen is the railway linchpin for at least four local lines.
The cost is 26 chf one-way
More info : Swiss Federal Railways
We drove as we almost always do. Parking without having Swiss coins was a slight inconvenience. Once we found the centralized underground parking,life became much easier.
This is a compact town easily navigated on foot. Obviously some of the architecture is old but the flavor is of a very modern convenient commercial center.
From Zurich HB (Main Station) there is every 30 min a train to St. Gallen and the trip takes around 1h and 20min, you can catch the train also from other stations. It starts at Geneva Airport and goes via Lausanne (or Bienne), Fribourg, Bern to Zurich and St. Gallen...
From Zurich AIRPORT you get also around every 30min a train and the trip takes 15min less than fromZurich Main Station...
If you come from Zurich (Airport) you can take the train, which will bring you in less than an hour to St.Gallen. Also by car you won't need more than an hour, unless there's rushhour...
Within the city of St.Gallen there's a very well extended bus-system.
Around the city, you can reach a lot of places by train.
by plane to the airport of zurich (http://www.zurich-airport.ch/) or to the airport of altenrhein (http://www.flughafen-altenrhein.ch/) and then by train (1h)to St. Gallen main station
Bus (PTT or local Bussystem)
The service is very good.
The tickets and the one-day card (6 chf) can be bought from the distributor at the station or in the bus.
From Zurich/Kloten (Airport) you need 1h 20 min to St. Gallen and you have to pay CHF 26.- for a one way ticket.