Go to San Mateo Medical Center (formerly known as Chope Hospital). You can even take the bus there from Half Moon Bay. This is the county hospital for you. The ER will provide you care, regardless of your ability to pay, as any ER must. The county also runs primary care clinics at this location and can set you up with services for free or on a sliding fee basis. If they offer services closer to you (such as med van or the Coastside Clinic, etc) then they will refer you appropriately. If you do not feel you need to go to the ER but simply want to see a doctor then I suggest trying to be seen at the Coastside Clinic, which is actually in HMB near you first (unless this is what closed and I am not aware). If it closed, then try the primary care clinic at the San Mateo location before the ER.
Their Coastside Clinic for primary care services was listed as follows:
225 S. Cabrillo Hwy, Suite 200A, Half Moon Bay, CA 94019 (650)573-3941 clinic open Mon-Fri 8am-5pm
Financial assistance hours: Mon and Fri 8am-4pm + Wed 3pm-630pm (This is when people are there that can help you with making financial arrangements or setting up Medi-Cal, but you can go there for care during any hours that the clinic is open)
If you need to go to the main hospital, the address is:
San Mateo Medical Center (for ER)
222 W. 39th Ave, San Mateo, CA 94403 (650) 573-2222 Financial assistance hours: M-F 8am-6pm; Sat 8am-4pm