i am looking at an edge 500 and i understand it has profiles for 3 bikes but will it do the following without issue:

bike 1- speed/cadence sensor
bike 2- gps only
bike 3- gps only

i would think it should work, but i dont want it constantly searching for a speed/cadence sensor if it is back home on the other bike.

I only have one profile on my 500 and use it on three bikes. There haven't been an issues for me.

do you run some with, and some without, the sensor?

Yes.

I have the garmin speed/cadence sensor on my road bike and just use the GPS on my cross and mountain bikes.

thats what i am looking for

road bike- sensor
neo vintage- gps only
cross- gps only

Correct me if I'm mistaken.... but don't the Garmins automatically stop searching for sensors after a certain period of time, and not search again until you either restart or otherwise tell it to search for devices?

anyone try one on 26mm bars? i dont think stem will be an option on my vintage or cross bike. both have "bladed" stems:

It'll work. I use mine on stems, 25.4 bars, 31.8 bars, etc. Garmin gives you a ton of rubber bands to mount the computer to pretty much anything feasible.

gah, i am probably going to end up spending more money...

Yes, it'll work just as you describe for the three bikes. I'm doing that right now with mine. You'll establish a profile for each of your respective bikes, and it'll include information such as the use of a cadence meter and so on. It won't search for them if you're set to use a different bike. Just be sure and make the switch in the computer before you begin your ride. I lost a lot of data for one ride because I'd failed to realize my computer was set to a different bike profile without cadence.

i ordered it. hopefully i wont have the issues some report...