That building is now the headquarters for the Phoenix Dream Center, a non-profit organization "committed to stopping human trafficking, educating tomorrow's leaders, and ending childhood hunger". In short, it appears to have been converted into a homeless shelter.
The "Tours" page on their website shows an aerial view that is clearly the same location - right down to the position of the palm trees!
Based on a Google Search of the address prior to that it appears to have been the "Comfort Suites Conference Center Hotel" and possibly prior to that the "Villager Premier Suites & Conference Center", although it's not clear if either of those were it's name in 1999 when you were there.