Here in my neck of the woods, we have a super-bargain matinee time -- where it's $5.50 for everyone ($8.50 if it's a 3D show). Otherwise, it's $9.25 for Friday & Saturday night shows, $8 for Sunday-Thursday night shows, $7 matinee shows from Sunday-Thursday. (Add in the $3 surcharge for any 3D movie showtimes.)
And the behavior problem does persist in the U.S., especially when it's a popular kids' movie or big blockbuster. (At times, I see parents bring in toddlers and babies in, which I despise.) In the small dramas or indie films, most of the audience members are very respectful. Being someone who does work as a doorperson (aka cleaning up theaters between showtimes), there are plenty of adults who are as messy or worse than families. It only takes a few seconds to throw your empty bag and cups in the trash can.
However, there is a great theater chain called the Alamo Drafthouse (mostly based in TX but is branching out in NY, San Francisco and VA) where the company has a zero tolerance policy for no talking or texting during the movie, only adults over 18 are let in (children are allowed, but must have parents with 'em), they serve food before the show starts, and it's universally praised as the best theater chain in the U.S.. If you manage to travel to the U.S., make sure you go to a location that has the Drafthouse.
Like mkiker said, go during the off-days in the week as early as you can. And if you have a choice between a 2D and 3D show, get the 3D. People are less willing to pay for 3D now if they have the choice, so there's usually less people there.
"Aliens conquering Earth would be fine with me, as long as they make me their queen."
- Gillian Anderson