It's a smart move for him. He needed to get it out of the way. Hispanics will not vote for Republicans regardless.
Only one GOPer has won the popular vote in the last 6 elections and that was GWBush in 2004, and the biggest swing group for him (compared to 2000 and 20008) was Hispanics (followed by Asians). He didn't And he got their support by supporting comprehensive immigration reform.
If Walker gets Romney-like numbers with non-whites he will need to match Reagan's numbers with whites to make up the dif and win. And running against Hillary, who should at least do better than Obama with white women, means that Walker will need ridiculously high numbers with white men.