It’s possible to drive the entire length of the Interamericana (often referred to as the Pan-American Highway outside of Central America) from North America to Panama , but this is a long, serious trek and there’s always some risk of encountering bandits, brutal roads, and dyspeptic border guards.
Making the trip requires serious planning and a well-equipped vehicle. Allow about three weeks from the Mexican border to Panama at a reasonable pace. Bear in mind that North American auto insurance policies don’t apply south of the border.
Cars rented in Costa Rica  cannot be driven in Panama, and vice versa. Even trying to drive cars registered in one of the countries across the border into the other is a nuisance and a source of continuing squabbles. It’s not worth the hassle for a short trip; take the bus instead.
RV convoys occasionally make pilgrimages down the Interamericana. The only true RV park in Panama is XS Memories (tel. 993-3096, fax 993-3069, www.xsmemories.com ) in Santa Clara, about a two-hour drive west of Panama City . It has 22 hookups for campers and mobile homes and can provide current information for those interested in shipping vehicles to South America.