Leave which airport Andy? Manila or Dubai? You can't leave Dubai unless you have a UAE Tourist Visa anyway. Although they do offer a 2 or 3 hour transit bus tour of Dubai for passengers who have long transit waits there, but you aren't allowed off the bus
I've never felt unsafe in the surrounding area outside Manila airport in daytime. I spent many a day killing time in Manila after I've checked out of my hotel and am waiting to leave for NAIA for a late flight. There's always something to do there, even if it's just going to the cinema in a mall