What are the best day trips from San Francisco?

Sonoma over Napa for a couples day trip, and it's not close. Napa's Highway 29 corridor backs up to 2-hour traffic by 11am on summer weekends, and the big-name wineries charge $50-85 per person for tastings in rooms that feel like airport lounges. Sonoma Valley is 70 km north, about 55 minutes on US-101 to CA-12 without traffic. The town square still has a public park where you can sit with dry jack cheese from the Vella Cheese Company and a bottle from Buena Vista, California's oldest commercial winery. Tasting rooms along the square charge $20-30 per flight. The couple dynamic works here because one person can browse the shops on East Napa Street while the other does a second tasting at Pangloss Cellars, and you're 200 meters apart the whole time. Dinner at the girl & the fig on the northwest corner of the square runs $35-55 per entree with an outdoor patio facing the old Sonoma Mission. Book for 6:30pm and you'll make it back to the city by 9pm.

The Muir Woods and Sausalito loop is the 4-to-5-hour option that works when one of you wants a forest walk and the other would rather sit at a waterfront table. Muir Woods is 19 km north of the Golden Gate Bridge. You need a parking reservation at recreation.gov at least 2 weeks ahead for summer weekends, or take the Marin Transit Route 66 shuttle on weekends for $3.50 each way. The 1.6 km boardwalk loop cuts through old-growth coast redwoods where the canopy drops the temperature 5-6 degrees Celsius. After the walk, drive down to Sausalito and take the Golden Gate Ferry back to the Ferry Building ($14 per person, 30 minutes). One of you gets a forest, the other gets a waterfront lunch at Fish on Harbor Drive, and you're both back downtown by mid-afternoon.

Half Moon Bay is 45 km south on Highway 1 and hits differently than the wine country options. The drive itself is part of the trip: Devil's Slide, now a pedestrian trail above the old highway, gives you a 20-minute cliff walk with unobstructed Pacific views. The town's Main Street has Sam's Chowder House for a proper lobster roll at $28, and Mavericks Beach is a 10-minute drive north if you want to watch surfers on big-wave days between November and March. Point Reyes is farther at 90 minutes but rewards the drive with Drakes Beach, the Point Reyes Lighthouse (308 steps down), and oysters at Hog Island in Marshall for $3 each at the outdoor shucking bar. Santa Cruz at 120 km south is the longest drive but the boardwalk, natural bridges, and the surfing museum make it a proper overnight trip at minimum.