Check
www.smatervegas.com for coupon codes for all the hotels in Vegas.
There is a completely different feel to Vegas whether you are on the Strip or downtown.
The MGM Grand is nice but it is so huge that your room is often a long, long walk from any other part of the casino (and the Strip).
Aria is very high-tech and nice. Monte Carlo and the Tropicana are somewhat older places but you can get a much better deal at those two.
Keep in mind that MGM/Mirage properties also charge a daily resort fee (usually $22-25/day) in addition to the room rate. MGM/Mirage properties (Bellagio, Aria, Vdara, MGM, Mirage, Monte Carlo, Luxor, Mandalay Bay, Excalibur, New York/New York)
Caesar's properties do not have a daily resort fee. Caesar's properties (Caesar's Palace, Paris, Bally's, Harrahs, Flamingo, Rio)
Although it is at the other end of the Strip from the MGM Grand, the Venetian is my favorite place to stay. It is not inexpensive but the rooms are excellent, as well as the shops and food.
What will you be doing at the casinos?
I go about 2-3 times a year for poker tournaments and can gladly give you more insight if you'd like. Feel free to PM me.