Hi
I haven´t been there by bike but taking public transportation and hitchhiking.
Costa Rica is very easy to travel. Friendly people. The road conditions are not always good, but one should get along. The climate can be varying in different regions: from dry to extremely wet.
In the NorthEast, I suppose there is a lot of boat transport.
In Panama you should take care of your money and bargain. If a price ie for public transport seems rather high check with an official if possible. Or get loud and complain. It should be extremely cheap and definetely cheaper than CR.
It is a wonderful landscape.
KATRIN*