Hi there. PrEP is recommended when a person is at "substantial risk" of acquiring HIV. The risk from a single event of unprotected vaginal intercourse with a woman who has HIV is only about 1 in 2500. This means you would have to have intercourse about 1250 times with this person for it to be a coin toss. Of course, if the person does not have HIV then you have nothing to worry about except the other STIs out there.
That said, here are the risk factors for heterosexual sex:
HIV-positive sexual partner
Recent bacterial STI
High number of sex partners
History of inconsistent or no condom use
Commercial sex work
Unprotected sex in high-prevalence area or network
The best approach here would be to see if your partner from the bar has been tested recently. If negative, this would be very reassuring, though you would still want to get tested yourself at about 2 weeks and 3 months. An HIV antibody response can be detected as early as two weeks in a few people and in more than 99.9% of people by 12 weeks. Testing earlier than 2 weeks is helpful if the test is positive, although it would need to be confirmed. It is not too helpful before 2 weeks if negative (as false negatives are fairly common this early.)
As for PrEP, your doctor or an HIV specialist might recommend taking it while awaiting testing. This is a judgement call based on all the involved factors. Risks of treatment are very low, so some doctors have a low threshold for prescribing it.
Let me know if you have any follow up questions about this.