When I used to work in retail I worked in an area that had a large Eastern European and Korean population. I would say maybe about half of them knew how to get by having a basic conversation in English. At first it was frustrating because it was hard for me to get their orders right but most of them were regular customers so as time went on I knew exactly what they wanted as soon as they walked in.
The younger generation I understand because I assume they recently moved here and are still learning the language. On the flip side I would say a bunch of them were in their 50s/60s who have lived in this country for 30+ years and didnt know a lick of English. I worked a basic retail job so it wasnt a big deal, but I dont know how they would be able to go to the DMV or open a bank account or something like that.
Disclaimer: Both of my parents are immigrants who came here in their early 20s. Theyve live here for 40 years and speak English fluently (although with a pretty thick accent).