How many attempts are made daily in the Phoenix, Arizona area for real
estate websites in spanish?

Good luck finding the answer to that. The most useful answer would
probably be in terms of how many regional Google queries there are for
specific search terms, and Google just doesn't give that kind of
detailed info out.

Alternatively, you could run a trial AdWords campaign that geotargets
that area and the specific search terms you deem most relevant. That
would give you some real live data on how many people you can get to
click on an ad as well as how often the ad was shown; the number of
searches will be something greater than that (though maybe not much,
if your ad ranks high enough and has a big enough budget to be shown
constantly).

Popular tools for revealing search term frequency generally don't have
access to Google data, and may provide stupendously different answers
than you get in real life via Google searches.

try to go to a domain registrant stats site and they can tell you how
many domains have been sold in that area. That will give you an idea.