Hi P.,
We had our daughter's Bat Mitzvah party at a place called Temptations Prime Grill and Bar. It's on Ventura Blvd. just east of White Oak. The owner, Moshe Hooman, was incredibly accomodating. The place is small, but we managed to fit ~120 people in it, between the inside and outside. (The inside sat 80 w/room to dance) Considering what other places were asking, his price was incredibly reasonable -- $55/person. BUT, this included a full open bar, all of the table linens, tax and tip, and the place is already very tastefully decorated, so you don't need much. He's open for private parties by prior arrangement. On Saturday nights he won't begin until 1 - 1.5 hrs after sundown (the place is kosher),which would be pretty late in August (about 9PM). The number is ###-###-####. BTW, I think his Persian cuisine is better than his American fair -- and he makes A LOT!
I can't help you with the entertainment -- A DJ will cost at least $1500. I don't know what a single singer would be. I'll try to dig up some of the websites I looked on for extra entertainment (like magicians, sketch artists, etc.) and get back to you.
The place where you can really reduce your cost is in decorations if you do it all yourself. I bought a lot of balloons wholesale online and had them inflated at Party City in the Fallbrook Mall. It was about 1/3 to 1/2 the price of buying them retail. I also bought mylar balloons at the Dollar Tree on Platt. If you save your receipt, you can buy them ahead of time uninflated, and then get them inflated the day of the event. I filled plastic baggies with aquarium gravel and wrapped them in mylar wrapping paper (dollar store) for balloon weights. For the rest of the table decorations, I spread mylar shred down the center of each table and sprinkled little chocolate mints and nonpareils. (These will have to be kosher if you end up at Temptations. Munchies, in Beverly Hills, has bulk kosher candy at great prices.)
We were put in contact with a friend of a friend who's trying to build a novelty business and he got us lovely laser-etched crystal paperweights with light boxes that doubled as decorations and party favors. They cost $3.75/ea and I printed up small stick on labels with my daughter's name, the event and the date and stuck them on the side. We gave one/couple. Decorations for 100 cost about $130 total, not including the light boxes, if I recall correctly. If you're interested, let me know and I'll see if I can track the guy down.
You can cut the costs on invitations by buying invitation kits at OfficeDepot or Staples, then make them yourself on the computer. 50 will cost about $60 - $70, which includes invitations, inserts, envelopes and thank you notes. We didn't use flowers, but I'll bet there's a discount flower mart in L.A. you can go to. There was one up in San Francisco that I used for getting flowers for my best friend's wedding years ago.
Good luck -- it's really challenging to do this kind of a party on a budget in L.A.! Becareful when you price places -- make sure to ask about all the hidden costs. Most places charge for the table linens, chair covers, tax and tip and DON'T include that in the bid price. Some places even charge for the use of the dishes, dance floor rental, and setting up your decorations.
And congratulations to your parents, and kudos to you for being a wonderful daughter!
R.