Have not set up my sytem yet to try things but I would like to know if this is possible. Simple setup,
HD cable box hdmi to receiver.
PS3 hdmi to receiver.
Receiver hdmi to TV.

Is it possible to use the tv speakers only, when we dont want to have the surround system on? Are the tv speakers disabled when the surround is on? I will be using the harmony remote, so are these just functions that need to be performed to get the desired sound?

I do not have any HDMI equiped receiver yet. From what I have been hearing, a lot if not all HDMI receivers will not pass audio/video when turned off. If that is the case, you will not have anything on your TV unless your receiver is on.

Just trying to make it simple for the wife, she really dont care about surround. I can probably hook up componet from cable box to tv and have that as a seperate function on the remote.

Yes it's possible. Some receivers such as the Yamaha v661 (HTR6060) will a allow you to choose whether the receiver will process the HDMI audio or your TV. You can program your Harmony to do this switch.

Other receivers such as the Panasonic XR700 and XR57 are even better. When the receiver is on, it processes the sound, when it's off it passes the sound to your TV. I wish all receivers did this.

Unfortunately the Panasonic is about 2 years old and doesn't seem to have a successor making it harder to find.

Easily done! In fact I have my gear setup just that way to accommodate family members who "just want to watch TV".

To do it that way you need connect each source device directly to the TV. However with most TVs will not pass through a digital audio signal, so for example, you may need to add a digital audio (optical or coaxial) connection from you HD cable box to your receiver rather than using digital audio out connection from your TV to your receiver in order to get DD5.1. The TV will usually only output stereo from a cable box signal. If you are getting over the air HD then the TV’s digital audio out will be DD 5.1 if the HD channel is broadcasting 5.1.

I have the onkyo 605, sorry I dont have things hooked up yet, will be moving to new house in about a month, just getting anxious to get it up and running. hopefully the 605 can pass the audio along, trying to keep down on unnessesary cables and the tv switching input sources. but with only 2 devices I may do as trekguy suggested.

If your wife does not watch premium cable channels, the easiest thing to do is to split the cable from the wall. One goes to the box and the other goes to the TV. In that case, she can still watch regular cable channels without even turning on the cable box.