effects of immigrants on the poor

NPR had an interview with international economic advisor Adam Davidson on the effect of large numbers of legal immigrants on the U.S. economy. He argued that they don't hurt the economy because they things they buy creates enough new jobs to offset the number that they take, and they keep prices low. He claims that low-wage workers are not hurt. He totally ignored the fact that there are so many immigrants from Mexico, that many low-wage jobs, and the low-level management jobs, now require employees to be bi-lingual in English and Spanish. This makes it harder for most low-skilled U.S. born citizens to get ahead.
Also, he said that the "average" citizen benefits about 1% from illegal immigrants, because they hold prices down. This sounds like all those other defenders of the current economy who talk about the economic situation of the "average" American, when they are really talking about the average for all Americans. The very small upper class is doing so well, it distorts the economic statistics.