Yes, they were aware. According to the Apollo transcript, Luna 15 was prominent in the daily news items that mission control shared with the crew.
In the transcript, timestamps are day/hour/minute/second; speakers are:
- CC = CAPCOM
- CDR = Commander (Armstrong)
- LMP = Lunar Module Pilot (Aldrin)
- CMP = Command Module Pilot (Collins)
23 hours into the mission (i.e. on July 17), we have the first mention of Luna 15:
00 23 14 09 CC 11, this is Houston. If you are interested in the
morning news, I have a summary here from PAO. Over.
00 23 14 20 CDR Okay. We're all listening.
00 23 14 23 CC Okay. From Jodrell Bank, England, via AP: Britain's big
Jodrell Bank radio telescope stopped receiving signals from the Soviet
Union's unmanned Moon shot at 5:49 EDT today. A spokesman said that it
appeared the Luna 15 space ship "had gone beyond the Moon." Another
Quote: "We don't think it has landed," said a spokesman for Sir
Bernard Lovell, Director of the Observatory.
Buzz Aldrin was probably the most interested in spacecraft trajectories among the crew, so small surprise that he was the one to inquire the next day:
01 08 53 58 LMP Roger. What's the latest on Luna 15?
01 08 54 02 CC Stand by. I'll get the straight story for you.
01 09 37 44 CC Hello, Apollo 11. Houston. Over.
01 09 37 48 CMP Go ahead, Charlie.
01 09 37 50 CC Roger. Latest on Luna 15 - TASS reported this morning
that the spacecraft was placed in orbit close to the lunar surface,
and everything seems to be functioning normally on the vehicle. Sir
Bernard Lovell said the craft appears to be in an orbit of about 62
nautical miles. Over.
Three days in, before the landing, another news item:
03 00 31 11 CC In Moscow, space engineer Anatol Koritsky was quoted by
TASS as saying that Luna 15 could accomplish everything that has been
done by earlier Luna spacecraft. This was taken by the press to mean
Luna 15 could investigate the gravitational fields, photograph the
Moon, and go down to the surface to scoop up a bit for analysis.
Much later, after leaving the moon, another daily news update from CAPCOM:
06 04 23 13 CC Luna 15 is believed to have crashed into the Sea of
Crises yesterday after orbiting the Moon 52 times. The Soviet News
Agency TASS reported that "scientific research in near Moon space was
carried out." Sir Bernard Lovell at Jodrell Bank Observatory said that
Luna 15 hit the surface of the Moon at a speed of about 300 miles per
There's no mention of Luna 15 in the transcript outside of the world news context; it's very unlikely they would have seen it. Space is big, exhaust plumes are small, rocket burns are short, and spacecraft windows are surprisingly dirty.