Can we eat in a restaurant that serves alcohol?

It is definitely better to avoid being in those places. Alhamdulillah, nowadays we have a number of restaurants that don't serve alcohol. However, strictly speaking, if you needed to be in that restaurant maybe for a business meeting or whatever it may be, the hadith collects by the Prophet (sallallahu alayhi wa sallam) said: 'Whoever believes in Allah in the Last Day, do not sit at a table where alcohol is being consumed.' So it's sitting at a table in particular where people are drinking that's where the prohibition refers to. So definitely better to avoid that environment, but strictly speaking then yes it would be permissible.