Latino Decisions, Mother Jones and others have been reporting that the major polling firms are underestimating President Obama's share of Latino votes because they are not polling in Spanish as well as English. And those US citizens who don't feel comfortable speaking English in an opinion poll are less likely to vote Democratic.
Latino Decisions has been polling weekly and is showing a 50%+ margin for the President. That result is consistent with other Spanish language optional polls. In the latest Polltracker average of all polls, the President is only winning 62% of Hispanic voters, a difference that is almost certainly due to the English-only format of those polls.
Hispanics cast about 12,000,000 votes in 2008 and are expected to cast an even greater number this year. But if we just stick to 12,000,000, the actual number of votes for the President at the higher estmate is an increase of 1,300,000 (the difference between 62% (Polltracker's current number) and 73% (Latino Decisions) for the President). There were about 130 million votes case in 2008 and if the voter turnout is similar this year, then we're looking at an extra 1% for Obama just from the undercount in the polling of Latinos.