What can consumers do if they've forgotten to make reservations at their favorite cafe? Nestle Frozen Food Co. suggests they try its newest frozen food line. Lean Cuisine Cafe Classics offers such restaurant-style entrees as Chicken Piccata and Grilled Chicken Salsa. "The specialty of the house is now at your house," say the two introductory TV spots, breaking today from Messner Vetere Berger McNamee Schmetterer/Euro RSCG, New York. A Sept. 25 free standing insert, national direct mail, and four-page October magazine insert will support. Impact, Chicago, is the brand's sales promotion agency.