You can never go wrong with Spain, the way I see it! Maybe go to AGP once that seasonal flight starts up? I'm not sure what kind of hiking is around (is a beach an acceptable substitute?), but everything else is pretty good. Being a beach town, you're bound to have some kind of lux/spa option available. That one wouldn't be you, would it? ... Food in Spain is, in my opinion, one of the most underrated cuisines in the world. Seville is also a couple hour train ride away, easy day trip (or maybe a night) and that has lots of local culture to check out - lots of history, and excellent night life (or day life, whatever life ).

One other possibility to consider. This is where my bias becomes even less subtle, but how about something in or around the Colorado rocky mountains? Nice central location from all 3 cities. Lots and lots of hiking/adventure out here, and I would imagine you could find a nice hot springs place if you look around a little! Food/local culture is not as thrilling as you'd get out of the country, but for something in the US it's not bad. Lots of mountain/ski towns have really neat personalities. Just be careful of the mountains in Spring. That snow doesn't magically disappear, so they call it the "mud season" for a reason! If you do that, consider spending a day or two in Denver so you can gradually get used to the altitude. Denver's 5280 feet doesn't bother me, but I start to feel just a little different when that number doubles! Oh, and if you fly in and out of DEN, give yourself plenty of time on I-70 coming back if you go on a Sunday. Traffic can be pretty nasty!