I hear about this a lot, but there are a number of states with few or almost no illegal immigrants, and somehow all the work gets done.

From this source, Maine, Montana, New Hampshire, North Dakota, South Dakota, Vermont, West Virginia, and Wyoming had fewer than 2,500 illegals in 1990 and 2000. There are other states on the chart with relatively small numbers, including farm states. Haven't looked for more recent data - I expect there will be more after the 2010 census.

Somehow, in all these states, hotel rooms get cleaned, lawns get mowed, and all the work gets done that "Americans won't do." Granted, the agriculture in some of these states isn't the hands-on type of thing you see in California, and there are other factors, but obviously the low end of the wage scale in many categories is getting filled.

Still, the article points out an important issue: low-end work that requires some experience. Many of the migrant farm workers do this every year, and know how to do it. As a teenager I did summer field work for the local cannery's farms, but it was something you could be trained into in twenty minutes.