Someone here in Belize would like me to order them a cheap unlocked GSM Android phone. Budget around $100-$120.

In that price range, I realize I'm pretty much limited to really old crap phones. What I want to know is, can anyone recommend the least crappy one?

would like:
somewhat stable and reliable
enough battery to last through the day with light usage
easily upgradeable to at least Android 2.1 or higher

Any suggestions?

Check on eBay for anything with "Nexus" in the name.

Eg.

http://www.ebay.ca/itm/HTC-NEXUS-GOOGLE-...=item416e99e1e9
http://www.ebay.ca/itm/HTC-GOOGLE-NEXUS-...=item3ccc4f4d7c

That really does seem like the best option. Can't find a new one for under $150 though (it's for a Christmas gift, so it has to be new and must be able to get to TX before the end of the month for its trip on down to BZE)

Dollar-no-object, you really don't want anything that can't run the latest Android versions. That says you want either the current Nexus 4 or the previous Galaxy Nexus. A Nexus S is the oldest that you might want, and that's starting to make compromises.

Poking around on eBay, the "buy it now" new-in-box Nexus S units seem to be going for $180, give or take. Used phones seem to be under $150, if you're persistent.

The Galaxy Nexus, used, seems to be clocking in around $250, which is pretty sad when a brand new Nexus 4 can be had for $299 directly from Google.

The Sony Xperia Tipo serves this price point and even has ICS standard:
http://www.newegg.com/Product/Product.aspx?Item=N82E16875212217

Step up to the Miro for $50 more, and you get a (slightly) bigger screen, better camera, and LED flash:
http://www.newegg.com/Product/Product.aspx?Item=N82E16875212219

Another option would be something from Blu. They often have a good bang-for-the-buck, but updates are very questionable. At least if Sony doesn't update your phone in the future, the Free Xperia Project is pretty active.

Well, for better or worse, I ended up with a Pantech P8000 and a HUAWEI Impulse 4G U8800. Both come with Froyo. I think the Pantech can be updated to Gingerbread, but I'm not sure about the Huawei.

I was supposed to come in around $200 for both phones and came within $ .98 of doing so. Ultimately, the buyer picked the phones. I tried to convince them to spend the extra to get the Nexus One, but when they make less than $25/day, it's a hard sell.