Is it safe to drink alcohol (one or two beers) while on amoxicillin and clavulanate capsules?

No guarantees: There's no major interaction with alcohol. That being said, when sick (the reason I'm assuming you are taking amox/clav) alcohol can delay recovery as well as interfere with productive rest/sleep. Amox/clav is broken down in part by the liver as is alcohol, so there is certainly potential for harm there especially with excess. I would avoid alcohol until feeling well and off antibiotics.