The don't call Las Vegas the Desert for no reason, bub. From what I hear, there isn't anything better than the drek I got at the Italian cafe in the Forum at Ceaser's.
CG has a US Western States forum, and there is a thread there, but, IIRC, there was no good news there either. Feel free to check it out, though.
If you plan on taking 95, instead of 93 through Lake Mohave, (but why would you?) there is a decent place in Bullhead City, believe it or don't. It ain't spectacular, but it's better than anything I've had in 'Vegas.
Fire House Coffee Co. 1371 Hancock Rd.
Rumours that I've heard about decent coffee in 'Vegas, but don't have anything to back them up are:
4550 S. Maryland Pkwy
918 1/2 S. 4th Street
Cafe Espresso Roma
4440 S. Maryland Pkwy
The Gelato shop downstairs at the Bellag'
Just outside the main doors of the Plaza Hotel
One Shot, One Kill