Central America for 6-8 weeks

Hi,
We are coming to the end of our epic RTW trip and have decided we would like to sample some of Central America for a return later when we have made more funds.

We will be travelling down from West Coast USA and back to Atlanta, and have between 6-8 weeks - August/September

We are seasoned travellers who like to explore and get to know the culture, love beaches and snorkelling, fairly simple hikes, and are real foodies.

Can anyone recommend places? Not sure how much time is needed, so far was thinking of starting/ending in Belize....

Is Belize to Costa Rica to far/too much to do? ....we don't like to rush.

Also, prior to this we are planning to buy a camper/van in California for 4-6 weeks (only cos they are too expensive to rent), is it feasible to drive down the Mexico coast and through CA? Could we sell it down there or would we have to bring it back to US?

All replies very much welcome!

Chris and Charly