Short trip to South America in January

Hello! My boyfriend and I (mid-20s) are looking for a way to spend 10-14 days in early January. We have been to Nicaragua twice and LOVED it -- our favorite places were Jiquilio and El Astillero because of the laid-back locals, empty beaches, and low prices. I'd love to go back to Nicaragua (or even move there for a year or two!), but it's time to stretch my wings a bit more, so I'd love to hear what everyone thinks of South American destinations.

Our budget is about $2000 per person, though spending less is always a plus. We could fly out of NYC, although Philly would be more convenient. We are looking for a beach destination that is not-crowded, SAFE, and has the possibility to surf (we are beginners). We are NOT looking for an all-inclusive resort or spring-break-like party! My boyfriend "kind of" knows Spanish, and I'd like to learn more than just basics so a Spanish speaking country is preferable...but we could be convinced to give Brazil a try.

Any information/suggestions/tips you can provide would be greatly appreciated! Also, we are willing to try somewhere in the eastern hemisphere if there are recommendations outside of Central/South America, although that might better left for a time when we have more vacation days. Thanks!