LOS ANGELES - A potentially powerful expatriate voting bloc likely will have little effect on Mexico's presidential race because of the illegal status of many who live in the United States. Thousands of Mexican expatriates streamed into border towns Sunday to vote in their homeland's elections and others were allowed to cast absentee ballots for the first time. Still, many more were disenfranchised by their fear of crossing the border as undocumented residents. "I really wanted to vote, but I don't have papers so I couldn't go to Mexico" to get a voter card, said Adriana Lopez, 27, a housewife...