(partial report since I didn't try all 30 options!)
Being currently employment-challenged, my SO and I headed to the Festival of Greece this morning, taking advantage of the free admission (until 4pm).
There weren't a lot of non-food booths, but that's okay, we were there for the food. Food was scattered around, although there was one "dining room" (on the left as you enter) that seemed to have all the offerings. Good views if you perch on the wall on the west (left) side.
We started out with a gyro ($5). The tzatsiki on it was very good, but the gyro meat itself wasn't impressive. This booth also had the longest lines of all (probably because of the recognizable food name!).
Followed up with some great spanakopita (filo bread filled with spinach and feta), $3. Definitely worth it; this was probably the best food we tried.
Followed up with loukaniko (grilled greek sausage wrapped in pita, mustard and lemon optional), $4. Good, but the suggestion at the booth was that it truly excelled if one went back to the gyro booth and added a side of tzatsiki to it... makes one wonder why they didn't offer it at the loukaniko booth!
Souvlaki ($3) was tasty, but minimal -- just a skewer with chicken or pork bits that was grilled. Not the most amazing flavor, but not bad.
The lamb chops weren't ready yet (we got there around noon, it had just been open an hour). As we left they were serving (3 chops and bread for $8, not bad), but we were full. Nor were the loukoumades (think "donut holes") ready, they were having mechanical problems.
Other offerings were souvlaki ($3), calamari ($6), lamb sandwiches (at $8, didn't look worth it). The dining room had a lot of other options including dolmates ($2), tourlou ($5? not sure.. a vegetarian stew), kalamari olives ($1), and other larger traditional dishes -- but had a very long line.
Drinks were disappointing. Wine $5, beer $4, water $2. I think there were greek coffee options, too. I'd suggest bringing your own drinks. No corkage fee! ;-)
Food seemed pricy given the small portions, but it's fun wandering around and sampling. Not haut cuisine, but given the sparsity of Greek options in the Oakland area, it was a lot of fun.
Parking is an issue. Coming from 580, I'd suggest turning off at Tiffin (the last through cross street before the cathedral) as all of the lots were full, even at the opening time on Friday! There are also shuttles every 15 mins or so to several nearby parking areas.
Fri-Sat 11-11, Sun 11-9. Most food spots shut down at 10pm (says the sausage booth guy). Dancing and music in the evenings.