I spent 14 months on South & Central. Fantastic and I really recommend. How will you travel around? If you won't have your own transport you will be somewhat on the tourist trail. The area is massive so you need to focus on what sort of stuff interests you. And how adventurous you are - some of it is very basic and under developed. Can you speak Spanish? You need to really, no-one speaks English unless you are in major tourist areas. Signs, even in very well known attractions, are usually in Spanish. The costs vary - depends on country and what kind of accommodation you will want. Spend as little or as much as you like really!

You could go to Ecuador - loads to do there - mountains, culture, Amazon jungle, then incorporate a Galapagos trip if you like wildlife. The Galapagos may look mega expensive if you look in a brochure, but when you are in Ecuador, you can go to an agency who will book you on a cruise for soooo much cheaper than booking from here (are you in the UK)?

We spent nearly a year in South and Central America, favourite countries were Argentina, particularly Patagonia (also the Chilean parts). Ecuador, so much variety, Amazon rainforest, Andes, coast is great too and varied. Quillatoa was a favourite area. Bolivia is so so different to anywhere, very old fashioned, lots of interesting history etc, lots of interesting trips there.
Peru is great but a really stark example of poverty meets mass tourism and all the issues that entails.

Central America we loved Guatemala, Tikal knocks the socks off Machu Pichu (not that it's actually a contest!), such a varied country. Nicaragua was also great, the corn islands being well worth a visit.
It's 10+ years since we were there, so lots will have changed we did it all by bus except one flight to Patagonia and flight from South to central. Brazil and Argentina were by far the easiest to get around, with Peru being a total pain, but worth it. Central America is great for "chicken buses" travelling with the locals etc.

Wherever you go try to get off the gringo trail now and again, and avoid the Lonely Planet top pick hostels. Lots of the gringo trail is great, and well worth a visit, but it gets pretty tiring after a while.

And yes, learn Spanish!

Enjoy 😁