Downtown San Mateo has a list of currently open restaurants which they update infrequently. The restaurants I've been to:

C Food Crush [/] - It's a crawfish type place. It's not really my thing especially with another seafood restaurant nearby.

Fusion Peruvian Grill [/] - The one time I was here it was an event night and I was the only one not there for the event so got kind of ignored by the waitress.

Jeffrey’s Hamburgers [+] - Jeffrey's is one of my favorite restaurants and they have huge milkshakes.

Little Sichuan [/] - I haven't been to Little Sichuan in years, last time was when parents were visiting.

New York Pizza [-] - I've ordered pizza from here. Was very average.

Noodleosophy [+] - I've only had delivered but both times were good. They make their own noodles. It's always very busy I think so the alternative is...

Noodles & Things [+] - Been here several times. It's a noodles and soup place and it's pretty good.

Pacific Catch [+] - A very chain restaurant but the food is good.

Philz Coffee [+] - It's coffee and I can't really tell good from bad. But it's got a neat and inefficient ordering process.

PorterHouse [+] - I think I've only been here once for a birthday dinner and it was pretty good. It's kind of an old place.

Urban Momo [+] - This place replaced Las Americas. It's Himalayan/Chinese food and was good the one time I've been there.

Wursthall [/] - Kind of chain-y like restaurant with upscale food. I ordered something that was a bit too non-traditional so it wasn't great.