I'd mention it, sure. For one thing, if he is against WLS, you want to know that so you can find another PCP like you did with the other one. And good for you, by the way, for finding a new doctor and looking for one that will support you.
Also, I imagine you want to get the ball rolling as soon as you can. So why wait to bring it up? Be up front with him, tell him you want to have WLS and want a PCP that can support you in your efforts to get healthy. Let him know what your insurance company needs and tell him what surgeon you'd like to use.
Disclaimer: I am not a doctor and do not play one on TV. I've done a lot of research on vitamins but am not qualified to give medical advice. I'm happy to share my research with you, but you should see a health care professional if you want medical advice.
Check out my blog at: storyofmyservicedog.blogspot.com/