On Fri, 04 Dec 2009 13:39:40 -0500, mm
wrote:

If I had, or borrowed, a GPS, global postioning system, would it also
show my altitude?

Depends on the brand/model.

Or, is there some moderately priced device that would show altitude to
say the nearest 10 feet?

Garmin ETrex hand held I own shows altitude if you desire.
Some models for street navigation may or may not.

Do they rent them?

Do who rent them?