Many commuters might not notice Wagner's as they whiz along Highway 7. The little red and white burger hut is parked on the southern frontage road, and you can't leave the main drag precisely at the spot--you have to exit early or late at Louisiana or Texas Avenue. But it's worth the side trip, if only for the rare experience of having carhops take your order and bring the food. The selection is broader than you might expect, including roast beef, BBQ beef, ham, reuben, chicken, fish, BLT, pork cutlet, turkey, and grilled cheese sandwiches. But dang it, it's a drive-in, so why not just order a cheeseburger basket with fries and coleslaw ($3.55) and a chocolate malt ($1.50 to $2.25, depending on size). Wagner's quarter-pound burgers are grilled to mannalike perfection; kick back and turn your radio up. Open from March to November; closed Sundays. Think you could eat a cheeseburger on a light-rail car?