If you don't like to drive in a foreign country or your budget is limited you can easily travel around Panama by bus.
Panama has a wide cheap network of busses. You can reach almost every location. The main companies providing comfortable double-deck busses for long trip.
In addition some small local companies using Coasters and converted school busses (colegial or diablo rojo) connecting the secondary towns and villages. In general they stop anywhere on their way if they have still available seats and you just have to make a sign to stop them.
Here you can find a rough timetable, ( check the 2 companies Panachif and Terminales David- Panama). Actually only the main companies doing Panama- David are scheduled there, so usually there are more options of those shown for shorter routes. In general you don't need (and you are not allowed) to book in advance the ticket. Just go to the terminal in the cities and buy it for the big busses. Go instead directly to the bus stop in the smaller towns and pay on board.
The busiest days around holidays they could be really packed of people, so leave early or, for long distance trips, think to travel with night express busses. In this case remember to purchase the ticket in advance if you are leaving from a secondary town in the night, to let the driver know if he needs to stop to pick people along the way.
Travel time from Panama City
David 7-8 hours
Almirante ( Bocas del Toro) 10-11 hours
Santiago 4 hours
Penonomé 2,5 hours
Las Tablas 4,5 hours
Colon 2 hours