If he wants some very authentic (and spicy!) Mexican Food, hit Los Dos Molino's. There is one down on Central Ave just on the edge of South Mountain Park.
There's another on the corner of Alma School and Broadway. They've got the hottest "house" salsa I've had. Their burritos and flautas are huge.
If he's jonesing for a good draft from your side of the pond, go no further than Rula Bula. It's on Mill street, just south of 3rd street. Here's the website:
http://www.rulabula.com/
Alice Cooper's in downtown Phoenix is a good place to grab a burger or rack of ribs.
Oregano's is on University just a little east of Campus. They've got great pizza and sandwhiches. Usually a great place to scope out some err...college scenery. Too bad school is out of session right now. If he's there for six weeks he might catch it just as people are getting in next month.
4 Peaks Brewery has some really good burgers and a very nice selection of micro-brews they make in house.
http://www.fourpeaks.com/
If he ever heads for the border (Mexico) be sure to stop in at Tubac(about 30 miles north of the border) and eat at Tosh's. It's a very good mexican restaurant too.