Will be backpacking at yosemite in the end of june, and was wondering if i will be free from misquitios if i sleep with only a quilt and head net (avoiding a bivy) i will be under a duomid.

I used that combo last year in Mt. Rainier NP, with very buggy conditions at some sites. I used the cheap Coghlan's head net, which has fine mesh (not so good for hiking in, but still seems to block bites even when against skin).

It worked, but the buzzing from the mosquitos was still an issue. Used earplugs for that. And I could see sleeping in headnet being claustrophobic for some. I wore my hiking hat under the net, which helped hold it off my face a bit.

I've done this a few times and it worked great. There is buzzing which is annoying, but then I didn't have ear plugs with me. I think you would probably be fine with the duomid and head net.