Travelling from San Diego to the Grand Canyon, Plaining on stoping overnight in the Phoenix area! Don't know anything about the area where is this best place to stay ie Scottsdale or Downtown Phoenix! just won't a nice safe area!

Are you simply driving in then driving out?
If so, I wouldn't bother going over to Scottsdale, which will take you well away from your route of travel (the interstate).
I'd also avoid downtown PHX for a variety of reasons.

If you'll be doing no touring of the metro area, find a hotel close to I-17 north, well away from downtown. The Sheraton Crescent is a good option.

If you're planning on touring PHX for a day or more, then yes, stay in east PHX or Scottsdale.

It is only about a 6 hour drive from San DIego to Phoenix, so you might want to continue farther up the road to either Cottonwood or even Flagstaff

I agree with the previous poster - If you are just passing through the Sheraton or Crowne Plaza (Not the one downtown) are good options as they are easy on/off I-17. If you are looking for something to do at night other than eat & sleep, the Tempe Mission Palms or Courtyard Marriott in downtown Tempe are good options - really the only areas in metro PHX with any kind of street life. The area also has many restaurants & watering holes, which you could walk to from your hotel. If you or any of the members of your party have not seen Sedona or Oak Creek Canyon before, I highly recommend the detour (Take rte 179 off I-17 exit 298. Follow it to rte 89A and follow it north to Flagstaff). It will add an hour or so to your drivetime (If you don't make any stops) but is well worth it. Have fun.

I would suggest the I-17 corridor -Metro Center, and north. Metro Center is at I-17 and Peoria Ave. There are many hotels in this area. And many good places to eat. Plus shopping at Metro Center. Easy back on the road again access. (Flagstaff is another 3 hours further)

Thanks everyone for your help! Have given me somethings to discuss and work out with with my travelling compaions!Really appreciate the help!

Circa, Flagstaff is just 2 hours north of Phoenix from the Metrocenter area, an easy drive up I-17. And you can see Sedona on the way, if you want some time to your trip north.

You can get a room at the Hilton in East Mesa for $30 a night on Priceline. It is a safe area right outside of Phoenix.

Except Mesa is as far off track as you can get from Anthony's route up I-17 north.
That would add almost an extra hour to his drive.