We went as far as Panama in a Montero and I've gotta admit, we had to seek out opportunities to use 4WD.
I guess a lot has changed down there since the early 1990's.
I spent the better part of a year driving, surfing, and wheeling, while on the way to Costa Rica and back... and spent at least half our trip on dirt/mud/sand tracks of all kinds.
OP,
If you want to hit jungle tracks, drive on the beach, and be able to go where ever you want, take the 4x4...you'll be glad you did.
Have a great trip...Cheers