One, you're not going to be "pentesting" starbucks wifi. On an actual pentest you're going to have a written contract from the company you're doing the pentest on, that will state what you can and can't do. No company in their right mind would allow you to spoof a public wifi network they don't own. If they do, it's still not going to cover your ass. Running a pineapple in a starbucks or any public wifi without the owner's, not the manager, the freaking owner's, written permission is illegal. You'll most likely be brought up on the state's wiretapping laws, and any other computer crimes laws the local DA can justify.