I can recommend Mexico (and second Raffles on this as I know he's a Mexico Champion).
I have been a couple of times and I loved it - it's an inexpensive destination, great food, lovely weather and lots to see if you're a 'culture vulture'. If you don't already speak Spanish it is a good to learn some as I found when you are away from Mexico City it's hit and miss at best as to whether you can find someone who does speak English.
I had the most divine hot chocolate while I was there which I've tried in vain to reproduce at home over the years - I got close by adding nutmeg and cinnamon to the mix but it still wasn't the same.
BAH