Fishing for an inexpensive way to unwind after work? Cast your lot with the rest of the downtowners who head to Del Mar Crab House, an inviting, below-street-level eatery in Larimer Square. There's no bait-and-switch here: Look for the $2 appetizers offered Monday through Thursday, and you could net a cup of soup, mussels, peel-and-eat shrimp, crabcakes or steamed clams (oysters are 75 cents each). And on Fridays, the snacks are on the house: The happy-hour buffet includes shrimp, hot wings, chips and salsa, jalape?o poppers and quesadillas. With well drinks, beer and wine all priced at $3.50, you can raise your glass to reeling in a real catch.