Ask friendly whether the whole table is booked and sit down. If they don't respond, just move their bag a bit and sit down. Keep looking friendly and relaxed,

Ask friendly whether the whole table is booked and sit down. If they don't respond, just move their bag a bit and sit down. Keep looking friendly and relaxed, signal that you're not a threat and everything's usually fine. It's not that difficult. (Escalated version: If they start complaining in an unfriendly way, mix your coffee with their laptop. Accidents happen in crowded coffee shops.)