By CEDAR ATTANASIO, Associated Press CIUDAD JUAREZ, Mexico (AP) — Roberto Escalona Moreno says he witnessed a double murder on the street last week near the hostel where is staying. The Cuban immigrant has been assaulted, and his friends have been shaken down by police, he says. Moreno, 22, is among more than 30,000 migrants who are pressing for asylum in the U.S. but are stuck in Mexico's drug- and