We estimate that 57 percent of the illegal alien population comes from Mexico, 11 percent is from Central America, 9 percent is from East Asia, 8 percent is from South America, and Europe and the Caribbean account for 4 percent. Of all immigrants from Mexico, 55 percent are illegal; for Central Americans it is 47 percent; and it is 33 percent for South Americans.From http://www.cis.org/immigrants_profile_2007
That's 69% from Mexico and Central America. Toss in South America and we're looking at 77% Hispanic illegals. That's a pretty significant number. Assuming it's correct, less than 25% are from elsewhere.