Across the bus terminal at Pagsawitan, Sta. Cruz. get a jeepney bound for Nagcarlan. Alternatively, you may proceed to the Jeepney Terminal near the Sta. Cruz plaza or public market and take a jeep bound for Nagcarlan.
From Manila, one has to take a bus going to Sta. Cruz, Laguna. (I haven't tried it because we always travel by car, but I was told there are bus terminals at Buendia-Taft and Cubao, QC for buses going to Sta. Cruz.) Then, get a connecting jeepney ride to Nagcarlan.
It is most convenient to travel to & around Nagcarlan in a private vehicle. The National Road, as well as secondary and tertiary roads are in good condition, except for short distance dirt roads that you will have to pass if you go to the waterfalls area. It is best not to bring a very big vehicle, as parking within the town could be a problem.
From Metro Manila, take the South Luzon Expressway, exit Calamba and drive towards the direction of Sta. Cruz. You have option to go to Nagcarlan via National Highway, turn right at Brgy. Calumpang (after Shell Gasoline Station in Sta. Cruz) or take a shortcut through access roads in Calauan or Pila. There is lesser traffic in the access roads which are concrete or asphalt, but the roads are narrower.
Going up to Nagcarlan is tricky so the best option is by private van. We usually pay around AU$50 dollars a day including the driver's fee when we last visited the Philippines. Nagcarlan can be reached in about 3- 5 hours, depending on traffic, road constructions along the way, the number of times you have to stop, etc...
A Toyota Tarago van is very popular in the Philippines, it is roomy and whether you got relatives who will hang around to come with you or not, it is best to rent a van, trust me! Don't get an ordinary car even if it is cheaper, you never know when some roads are full of potholes or not, but just to be sure!Plus, you can stretch your legs after a few hours or so! My sister rode on her own car with her two kids and hubby and sometimes it was hard for them to negotiate some steep paths!
So it is best to get an air conditioned van as the roads are also dusty outside Manila though they are not mostly rough, just the fumes from the tricycles, jeepneys and buses will be annoying after a while!