Hailey Baldwin enjoyed a low-key birthday weekend ... and we're not surprised!

Hailey enjoyed a lunch date with hubby Justin Bieber on Friday at Nobu Malibu, after a good yoga workout and a smoothie with pal/stylist Maeve Reilly. Then when the couple got home, Hailey was surprised with gold foil balloons reading, "HB 23," in honor of her 23rd birthday.



The celebration didn't end there ... on Saturday night, the couple hit Barney's Beanery in West Hollywood with their adorable pup Oscar where they met up with some friends for dinner and drinks. Hey, they're not the Kardashians! Justin's not gonna invite half of LA to a big blowout with a them and a red carpet, etc., etc. -- these two are just kinda ... normal!



And previously, on Friday night -- again, normal ... dinner at home with wine and a cake. And oh, not so normal? A diamond-encrusted Audemar Piguet watch. Hmmm ... $150K?