Prepare for frustration when searching for the Signature Grille & Bar, tucked away in the Riverfront Towers off Jefferson near the Joe Louis Arena. After stopping at the security gate to obtain permission to enter the complex, you have to master instructions about where to park and how to find the restaurant. Signage is minimal to nonexistent. But when you finally make it to your destination and marvel at the magnificent view of the Detroit River and Windsor available from every table, you’ll know the trek was worth it. If you drop in at Signature for lunch or a light supper, you can choose among eight sandwiches ($8). Heartier eaters will find much to satisfy themselves among the 10 entrées, including Australian rack of lamb, broiled Norwegian salmon and barbecued baby-back ribs.