Before ordering onions I would like a ballpark figure as to how many there are in a five pound order.  Thank you.

Chuck, Each pound has about 20 onions, so a five pound order will give you approximately 100 onion transplants.

April 26, 2013
My Walla Walla transplants have been in the ground since November. They have all produced flower seed heads. Their necks are thick and healthy, sitting in the California sun all day. Will they ever produce big edible bulbs? Thank you for any suggestions or encouragement.

Your bulbs will be edible, but not large and probably should be eaten as soon as possible.
Flowering usually only occurs on two year old onions (ones left in the garden after harvest) since they are trying to complete their life cycle and go to seed for reproduction.  Flowering of one year old onions is most often caused by fluctuations in temperature over the growing season.  If they have the opportunity to grow, become dormant, grow some more, become dormant - in response to temperatures -  they will respond as a two year old onion would and try to seed. 
Even cutting off the flowering stalk will not help the bulb to get much larger since the plant is now putting its reserves into reproduction rather than bulb growth.