It is risky to send it without the I-693. Sometimes they immediately reject the I-485 because there is no I-693, other times they send an RFE to request the missing medical. So send it together unless you have a long delay with obtaining the I-693.
If the problem is that you can't get an appointment soon with a designated doctor, try to get a walk-in. Some doctors will accept you if you show up at the office and they don't have a large set of patients that day and you are willing to wait. Or you can try for an appointment with a doctor in another city or state.
If you don't send in the medical before the interview, you probably won't get an interview.