enable prefixes?
 

I'd like to force users to select a location when posting in the classifieds - it may go in the title to help searching. I'd like to give them about 100 cities to pick from and if somebody puts that in the search field it will filter. Is this possible or are there any suggestions?

Well there is functionality for that in some manner. For example under Admin edit categories the first 6 normal text input fields if you fill out one will be required and if someone tries to not input a location it will not allow them to continue.

This of course is not going to be a dropdown box nor would it prepend itself to the title in displays. That would be code modification.