Entering at Los Chiles, leaving across the Panamanian border. A travesty, I know, and perhaps we can stretch it to six days, but what would be an absolute must? Budget modest but not tiny, we decided to spend time in Nicaragua rather than CR, rotten fruit expected!

If you're entering at Los Chiles, that must mean you're doing some island-hopping in the Lago or some great off-the-grid stuff in Nicaragua... Nice! Since you're entering up there, check out the Arenal Volcano area... You can take a San Jose-bound public bus from Los Chiles and hop off in San Carlos/Ciudad Quesada where you catch a bus to La Fortuna/Arenal (or hire a private taxi direct from Los Chiles).
From there, it all depends on where you plan to cross into Panama. If you plan to do so on the Caribbean side near Bocas del Toro, then take a bus to San Jose and another to the Puerto Viejo/Manzanillo area on the Caribe (or an interbusonline.com or other shuttle door-to-door for ~$40/pp) and explore around there for a few days before crossing the border at Sixaola. If you plan to cross at the Interamericana Highway, it might make sense to check out the Osa Peninsula -- but it's going to be a long-ass haul first to San Jose and then down to Puerto Jimenez unless you fly...
