There are people in my neighborhood who have their two dishes mounted side by side on a stuccoed wall on the side of their house. I mounted mine on an eve on a side of the house not visible from the street. There are plenty of options as long as you don't have tall trees or other obstructions in the way. Here in the LA area the look angles for 110/119 and 148 are quite high so no problems even up in the mountains with lots of trees.
No problem as long as you have the right switches to go along with it. You might want to call back and verify what is included. I think they are charging $99 for the second dish if you just order it for HD programming.
By looking at the subject it made me think of what areas received the Dish500 signal (110 and 119 orbital slots).
I dont think the Dish500 will be able to pickup all the HD channels as some are on the wing slots although I have heard an announcement that the Dish500 would be all that you would need. I would tune in to the Consumer Charlie Chat on Channel 101 on December 8th at 10:00 PM for more information in regards to this.