First of all, a majority of Latinos in both these states voted for Gore.
The Latinos in Florida who vote Republican are Cubans, and they're about as loyal a Republican voting block as you can get. Getting tough on immigration is likely to increase their support for Republicans rather than decrease it.
In Texas, Bush has such a large percentage of the white vote that he can afford to do badly with Latinos. Most Latinos in Texas who vote Republican have been there for generations and have views on immigration no different than most whites.
Add to that the fact that getting tough on immigration will greatly increase the Republican share of the white vote, and it's a win-win.
The harsh, un-PC truth of it is that when Republicans do well with whites, they win. When they don't do well with whites, they lose. Swings in the minority vote just don't matter much.
Just look at the numbers. Latinos are 7% of the electorate. Suppose Bush were to capture an additional 10 percentage points of the Latino vote. That would get him a whopping total of 0.07% points more of the overall vote. It's chump-change.
By contrast, Steven Salier at Vdare showed that with a mere 56% of the white vote, Bush would have won the election (both the electoral and popular vote) even if every single minority voter went for Gore.