It's a great question, Jonathan ... and as far as I can tell, the answer is: it depends. If you're claiming the property as a local business (which you should be), the location will automatically be in the URL until you claim a custom username.
When claiming a username, I think it's best to choose a short name that's easy to remember (and one that's consistent with your community's username on other sites). I'd rather make the site easy for people to remember and use other applications and inbound links to make the search engines aware of the specific location.
There's a second issue to consider here, which is that more people are using the search function on Facebook itself, and it's clear from their latest redesign that they will push this as much as they can. So far, it's largely unclear whether Facebook users are searching for the same types of things they typically search for on Google (e.g. apartments in Atlanta), but it stands to reason that more people might start using these types of searches as they spend more time on the site.
Here's the interesting part about this: Facebook is testing various ways to present "social search" results. Not only do they suggest results as you type, but they also add more weight to results from pages and groups that you and your friends are connected to on the site. So now you need to have a page that's relevant to the search engines,
and you need to continuously develop your community to grow your audience and get your page in those "social search" results. Fun times, don't you think?
They keep updating their platform all of the time. I brought this subject up purely from what I was experimenting with regarding Facebook searches. Outside of the social circle, it still homes in on the title of the page relevant to the keywords you search for. The page title and name can only be so long. Perhaps there will be room for an open twitter discussion on #aptchat regarding how to attract traffic to FB pages from a geographical perspective.
