ATC can omitt the traffic pattern information if it's left traffic. So, if 2500 feet is pattern altitude I would, barring any unusual circumstances, enter a left downwind leg midfield to the runway advertised on the ATIS. Then tell the tower that you are entering left downwind midfield to runway xx.

Of course you need to scan and listen for conflicting traffic and adjust accordingly. If the pattern is totally saturated you might choose to do a 360 outside the pattern until you can safely enter and/or make contact with the tower.

Lots of variables, but at some extremely busy GA airports if you call the Tower outside of class D and advise them that you have the current ATIS, they may just respond something like: "N12345 report downwind."

There's probably no perfect answer to your question because there are lots of variables. But, because ATC told you to stay at 2500 ft, I would remain at that altitude and well outside the airport area. When I'm able to contact the tower I would ask for further instructions.

By the way, if the airport/runway uses left traffic, ATC can omit the traffic pattern information (e.g. enter left downwind).