I've been to 3 Targets in Vegas and in order of preference:
1) Rainbow Blvd: easy parking, store's never crowded, Greenland Market is across the street (so I sometimes just walk to/from Greenland to buy what I need)
2) Charleston Blvd: conveniently on the way to Summerlin Costco but this Target and its parking lot can get crowded since it's in a strip mall
3) Decatur Blvd: I don't care for the clientele