Just dial 9-1-1. AFAIK calling that # will GPS your location to dispatch even if you've disabled that function on your phone. Might not work on a foreign phone, though. Depending on the town they may or may not dispatch a cop to your location. I wouldn't hold my breath in like 99% of the cities.
Things have changed drastically here in places like NYC, Frisco, Denver, etc. You're not safe anymore.
If you come here these days I'd strongly advise formulating a "go to Hell" plan in urban areas. I/E- What to do if you get split up, quick phone access to emergency services, maintain situational and geographic awareness(street names, landmarks etc), designate a leader, and don't stray off the beaten path.