So many options!
So, given your spanish skills and interest in the outdoors, my first thought was somewhere in Central or South America. Here are my reviews of places I've been:
Peru would be a good bet - lots to see (surf/beach stuff on the coast, go up to the andes and check out machu picchu and other Incan ruins, then spend some time in the Peruvian Amazon) all in the same country. It's very travel friendly. If you do Peru check out Choquequirao - an incan city that is similar in size to Machu Picchu but requires a 2 day hike in and out, so it sees far less visitors. While Machu Picchu was a zoo, we had Choquequirao entirely to ourselves, and we saw a Puma and a condor there.
Most people will tell you to go to Costa Rica, and it is pretty, again with beaches and mountain rainforests, a good diversity of stuff. We spent a month volunteering in their national parks, and they are very pretty. It is also extremely touristy and expensive relative to other latin american countries. We did not make it to the Caribbean coast, but I've heard that side is less touristy. I also found it the most boring of all the latin american countries I went to in terms of food and culture, and it was the only one we've been robbed in. So Costa Rica gets a thumbs down in my book, it was fine but other places were better.
My absolute favorite place was Colombia. Don't believe it's rep, it is very safe for travelers provided you don't do something stupid like try and hike into FARC territory. It was so cool, and the people were so friendly. They don't get a ton of international tourism, so people are less likely to try and scam you or treat you like an ATM. We had situations where we left a tip and had waiters chase us out of the restaurant to give us the money we forgot. But there is a lot of internal tourism, so it is easy to travel around, and there are plenty of accommodation options. We spent 2 months there in 2008, and it was so great. The city of Medellin is really cool, perfect weather year round, sophisticated public transport, great museums and plazas and parks and night life. We loved Cartagena, a tropical colonial city on the coast. Near there is Parque Tirona, one of the most gorgeous national parks in the world, with jungle hikes leading to white sand beaches. We also went swimming in a mod volcano. We went white water rafting and hiking in the forests around San Gil. We also did a lot of hiking in the Coffee Zone, and stayed in some gorgeous little colonial towns (I think my favorite was Salento). I can't rave about Colombia enough.
Antigua, Guatemala was also really nice. It's 45 minutes from Guatemala city and a world of difference in terms of safety. Antigua is a little colonial town in the mountain, nestled between three volcanoes. Its up high so the weather is pleasant even in the summer. There is good hiking and hot springs in that area, and you are close to Lake Atitlan, which is a huge lake in the mountains surrounded by very pretty villages. Guatemala also has jungles with mayan ruins not far from that area.
Somewhere I have never been but would like to go - Patagonia. But given that you'd be going in winter, maybe not.
I hope that sparks some ideas for you!