Millbrae has a large multi-modal Millbrae Transit Center near the intersection of El Camino Real and Millbrae Avenue providing service to BART , Caltrain , and SamTrans. This is the terminating BART station for trains going south from San Francisco. There is a BART spur to the San Francisco International Airport (SFO)  just north of the Millbrae Station.
You can catch a Caltrain at Millbrae for points further south on the peninsula (a few travel down to Gilroy). Caltrains going north from Millbrae all terminate in San Francisco at 4th and King Streets. If your destination in San Francisco or your point of departure from San Francisco is anywhere near the 4th & King Caltrain station (near the South Beach area of SOMA), you should take the Caltrain rather than BART. The Caltrain trip between San Francisco and Millbrae is 18 minutes ("baby bullet"), 20 minutes (express), or 31 minutes (local). BART takes 36 minutes to San Francisco's Montgomery Station, and Caltrain is a far more pleasant ride. However, Caltrain takes more planning; it runs less frequently with more limited hours than BART.
The San Mateo Transit District, samTrans , provide bus service around Millbrae and beyond.
Millbrae Pancake House 1301 El Camino Real, Millbrae, CA 94030-1410, (650) 589-2080, Open late. Great American food and wonderful brunch.
Yumi Yogurt 1069 El Camino Real, Millbrae, CA 94030, (650) 692-9864, An amazing Bay Area chain with delicious flavors including cookies and cream soft serve yogurt.