We spent 2 weeks at the Fiesta grounds this year. We got there the Tuesday before everything started and left the Tuesday after. For days outside of the festival days, the nights are 1/2 price (at least for the boondocking spots). I wouldn't stay until Tuesday again- but Sunday, the RV parking greatly thinned out; by Monday, there weren't many people; and on Tuesday, we were literally one of the last people left.
I never figured out the whole story for water fill ups. It sounds like you're supposed to pay for a fill up but then it sounded like that was only if you had the truck come to you. If you had a bladder, you could go fill it up - I could never figure out if you were supposed to pay. We cheated. Our group was right across the street from the electric + water sites, so we would string hoses together and just top off our set of rigs OR I'd go to a friend's site who had water + electric and would fill my bladder.
For dumping, they'll either come pump you out or you can drive 5-6 miles up the road to a gas station with a dump station. I have a sewer bladder and did that. Friends had 55g drums in the back of their trucks and did the same. Folks in our group would use each other's gear and help each other out. I think very few people paid for pump outs.
To get from the RV parking to the Fiesta grounds is as mentioned- there are shuttle stops in the RV park and a crap ton of busses service them. They'll often drop you off at the end of your row and a lot of times even picked us up at them. We did walk back once at the end of the night as the bus pickup line was atrociously long. We probably had 8-10 adults and as many kids- the walk seemed like it was a little more than a mile.
We did learn that you can't drive back to the RV parking after an event lets out for 30 minutes. They turn the roads one way away from the fiesta fairgrounds. We were literally directed into a parking lot and told to sit tight by a cop who was directing traffic.
Before the Fiesta, we stayed a couple of nights at High Desert RV Park on the west-side of Albuquerque. Decent place and fairly inexpensive. On a previous visit to Albuquerque, we stayed at the Coronado Campground in Bernalillo - this is the county campground on the river. Nice place, but no sewer.
That said, if you can boondock- I wouldn't stay anywhere but on the RV parking grounds. The access was just too convenient.
Ton of pictures here: