Although not necessarily cheap, I would give another nod to the Camp Chef portable screens. I got a great deal off of Amazon on our 12 foot one.
We have had several movie nights (A Christmas Story, Despicable Me 2) at one of our local state parks. The park even lets us use an unoccupied camp site for the showing. We made sure to invite the entire campground to the movies, as even though not a lot did come...NOBODY complained since they were invited in the first place.
We have done this all during the colder months and when it got dark earlier so the movie wouldn't go past quiet time in the park. I also haven't tried it yet in the warmer months to see if the projector light attracts bugs down here in the Deep South.
The reason I really like the Camp Chef OS-144 is the rear projection capability. When showing a movie with a larger crowd, and normal forward projecting, people have to sit to the sides really so when they move around (as they will get up a lot) they don't get in front of the projector (unless you have a way to mount the projector high). The OS-144 has a removable back side, that once you un-velcro it, you can set up the projector BEHIND the screen for rear projection. The EPSON projector I have, has a setting that you just change on the projector that reverses the image for rear projection. This way the projector is behind the screen and the audience can sit directly in front of the screen, and won't interfere with the projection.
I place the projector, dvd player, and a cheap audio receiver with long speaker wire/speakers (you need to have good sound to hear it outside) on a table behind the screen, where it's all out of site, and out of the way. The black back that you undo to allow rear projection, you then just let hang down underneath the screen and it blocks all the light from the projector that the audience might see from underneath the screen......depending on the viewing angle. It all works fantastic.
I have some pics somewhere and will be glad to show you if you like.
Like I stated earlier, it's not necessarily the cheapest route, which I also wanted to go with originally, but I am glad I did spend the money, and get the OS-144. Another benefit of it, especially with it's own frame and such , is when we set it up inside the house a lot when my son has overnight company. You haven't seen more happier kids when they get to play their video games on a 12 foot screen.....by hooking the game systems thru the projector.
I kept watching, and caught it on sale from Amazon during the off-season for $170 with free Prime shipping.
How to Set Up Your Outdoor Big Screen 144 - Camp Chef - YouTube