Bocas del toro, car rental?

You can rent a bike, it's a lovely way to get around, heaps of people do it. Also, there's a public bus that goes up the road to the other end of the island. Not sure about frequency.

How big is the island? Are we talking about biking many miles? For example if I wanted to get to Bluff beach or Boca del drago?

There are a couple of ATV rentals with the most popular one being Flying Pirates. They also rent some other types of vehicals as well. To get from island to island there are plenty of water taxis and kayak rentals. The bus that goes to Boca Del Drago costs 5 dollars round trip and goes every 2 hours. Although I guess it is possible, people don't really rent out boats. There are tons of areas with shallow reefs that you could get in trouble with if you don't know the waters.

It's easy to get to Starfish Beach on the bus. You just catch it in town near the square, heading north. Just ask anyone, "Playa Estrella"? Seemed pretty frequent, but I don't recall how often. At the end of the road you can either take a small boat or walk to the beach. To get to Red Frog Beach, you negotiate a rate with one of the many small boat captains. But book it only one way; you can always call the captain on his cell if you want a ride back, but often you can attach yourself to other groups to get back and contribute to the cost. Wherever you are staying can give you all the help you need.

Rent a bike! Cheap, like $5 for the day. The road from town to Bluffs beach is lightly trafficked, and flat. Even with dirt/sand roads at the end, it only takes maybe 30 minutes, and it's beautiful the whole way. Stop at Packi Point for a beer if you need a break.

Not sure if you'll be able to see this, but here's a video clip from our bike rides from Bocas to Bluffs: https://www.facebook.com/photo.php?v=10201259903207131&set=vb.1458369428&type=3&theater