I Need of a Total Refresh
I tried to stay at the Hilton Mission Valley as I was hosting an event at the hotel in the conference center. The event was great, but the rooms leave something to be desired.
What I liked: not much. The service was average, the lobby area was clean but dated. The location, however, is good.
What I disliked: half of the hotel rooms overlook Interstate 8. I asked some other tripadvisor reviewers of this hotel how the noise was, they said it was tolerable. I found it to be too loud. I ended up leaving the hotel and going to the Doubletree (newly remodeled) to sleep, keeping my event at the Hilton MV. I found the parking system to be questionable at best. I had paid for parking but the meter outside didn't take the card. 
If you stay here, do not stay in odd number rooms, regardless of floor number. I was on floor 14 (top) and the noise from the freeway was almost 20db higher than at the Doubletree in the room (using a sound meter on my android phone). 
In Summary: I don't plan on coming back. It's fine if you can't find anything else, but I would not recommend this hotel.