Christians are everywhere in disguise, we learn to not judge by outward appearance or in a moment, a first meeting or introduction or a good or bad moment in life
Starbucks, in my opinion and feeling is a good environment compared to some other places you can choose to be these days. Even if you don't like, don't want, or cannot afford their coffee it is free, with comfortable chairs, wi-fi internet hook-up, and warm and air conditioned. You can enjoy without spending a dollar and meet new people, and find out if they are christians, or recruit them and lead them to christian faith.
Ok, not something I would do, too bold, but maybe you or lots of others on this earth are, more outgoing and bold.
Good Luck.