I take it you don't have a custom recovery installed and/or the ability to install/launch one (with a possible restorable Nandroid backup)? That would get you the ability to adb into your device to at least re-edit the build.prop file back to it's original state.
Barring that, even if you had previously turned USB debugging on, a wonky build.prop edit induced boot loop is not likely to have gotten to the point of launching/enabling the adb daemon for you to try to fix.
Not many (any?) options that I can see or think of, unfortunately

.