We've been to Luna Red a few times, and now make it a planned stop whenever we visit the San Luis Obispo area.
They have a very nice indoor dining room, but the real treat is to sit outside. Their patio area is pleasant and reasonably quiet. Well-placed umbrellas provide areas of both sun and shade.
Service has ranged from good to outstanding. The food is always excellent. We've had salads, lamb, chicken, quinoa waffles, bean soup, great fresh salads, and terrific sandwiches.
Please note that while the food is outstanding, the portions are not large. We find them satisfying but others may be wanting for more.
Parking in downtown San Luis Obispo can be a little challenging depending on the time of day and day of the week. In the downtown area most of the parking meters are either 30 minute or 2 hours. The two hour meters require coins (as of this writing it is $1.25/hour for the meters). There are also a few covered parking garages where the first hour is free. On days when there aren't a lot of visitors to SLO, you can find free street parking within 6 or 7 blocks of the restaurant.
Luna Red is worth a special trip.