Cruz does not believe in 'unlimited' legal immigration. For one thing, that doesn't make sense. Legal immigration has had targets annually for decades. People still have to apply, go through the process, get approved. They don't just walk up, introduce themselves, and get in as a legal immigrant with proper paperwork.
Cruz does believe in legal immigration. But, for that matter, so do I. I think there should be less of it now than there was 20 years ago, and I think there might be more of it 20 years from now.
You cannot find a quote in which Cruz says anything similar to "I believe in unlimited legal immigration."