I can't advise you on TM and mosquitoes in the Spring, but you're right that a
quality screen house will cost you
some $. There are several good models out there, myself, I bought a Eureka Northern Breeze several years back.
What I like about this model that many screen houses lack: a full zip-down cover over each of the screen walls (that
also double as awnings as well, poles are included for this). If you ever are sitting in the screen house in a driving rain
storm, the zip-down storm flaps come in handy. In the USA, they only sell the Northern Breeze 12 x 12 ft. model,
so I ordered mine from Canada, where they also sell a smaller 10 x 10 ft. size (which fits better in some of the tighter
campsites in Yosemite Valley). I love it, very well made, and great for the Spring, Summer and Fall.