Where would you go in the Americas in Sept/Oct?

I have all of September & October with no plans as of yet.

I’ve spent a lot of time around Europe and Asia in the past decade, so I’m not thinking of going to those continents, and I am heading to Central America soon for 7 weeks.

That being said, where is a good country or two or three to go backpacking during September and October? No rainy / monsoon season or cold weather please).

I’m thinking perhaps Chile, Argentina, or Mexico. Haven’t been to any of these but I have friends from each and I’ve heard amazing things from them. Any insights if you’ve been backpacking there?

Would prefer hiking, beaches for swimming/surfing/freediving are a plus but not necessary, but also a good blend of culture and history is ideal.

Budget is moderate backpacker level, probably no more than $3000 as I might be doing work exchanges too.

I do speak Spanish at a high conversational level and like traveling solo, prefer interactions with locals as opposed to backpacker party sites.

All suggestions welcome.