It's hard to go wrong RLBarker, there are so many great options that you're better off deciding which country you'd love to spend time in and then zeroing in on towns within that country with good language programs.
That said I think Panama, where I live, is a great option. There's a Spanish school in the capital's colonial sector, Casco Viejo, that gets great reviews and the owner has spoken at IL Event in Panama so we know the school is real (IL's annual Fast Track Panama conference), see https://cascospanish.com/.
Many say the easiest Latin American Spanish accent to learn in is Mexican or Colombian. I find the accent in Panama City to be very straightforward, it's not sing-songy but rather more like newscaster accents.
Outside of Panama City if you get into rural parts you will find that people speak a bit differently (clipping words/omitting the end syllable, for example) but this is true in much of Latin America (easier for learners to understand "posher" accents in cities versus rural parts)
If you love countries like Argentina and Uruguay then that's a quite different type of Spanish so you'd maybe want to go to a school that can teach you Rioplatense Spanish. And if you fancy spending a lot of time in Spain, same thing - it's a quite different version Spanish, probably best to study it in Spain itself.
~IL Panama Editor Jessica Ramesch