Uber has arrived on the Pacific Coast, destinations as Liberia, Nicoya, Manuel Antonio & Jaco are now Uber friendly! You can go to the beach easily and at a cheap price.
Now, because it is a very new destination, the driver/customer ratio will not be as high as in San Jose, but it is just a question of time and more will show up to the area.
For Manuel Antonio, public transportation is still well developed, and you can take the bus that comes every 20 minutes and takes you from Quepos to Manuel Antonio Park, with many other stops along the way! The ride is very cheap (335 colones or less than $1).