I mount my speakers on the wall with these:
http://www.sweetwater.com/store/detail/SS7913B/
You can take them off if you want to go somewhere. The PR-12 only weighs about 22 pounds, so it is easy to carry.
The mixer goes in a mixer bag ($40 from WorldTour). One more gig bag for mics and cables and you have it easily portable.
For instance, I am going to toss the equivalent setup in my trunk tomorrow and help a friend out with his party. I have more elaborate setups, but the PMH-3000 and some PR-10s (I use the 10" and a sub instead of the PR-12) is portable and will take me 5 minutes to set up. And it will be far better than his old VocoPro Duet.
My whole list for tomorrow:
Audix OM-2 wired
AKG WMS40 wireless
Behringer PMH3000
Peavey PR-10 pair
One speaker stand, one mic stand
Two mic cables
Two speaker cables plus two Speakon/1-4" adapters
Laptop with Compuhost
1/8" --> two 1/4" sound cable
S-Video --> composite adapter and cables
It all fits in one mixer bag except for the speakers and stands. It won't take up even half of my large trunk.