May help answer some of your questions.

Here is a link that might be useful: Other member asked similar question

This is our 3rd season for concrete block square foot beds. We use the heavier (for stability)concrete ones which cost $1.00 apiece last year from a local supplier (Home depot and Lowe's were a little more expensive).
First year we made 4x8 beds, 2 blocks high. To get 4x8' interior space it took 40 blocks (seven each end and 13 each side, overlapped). Also used 18 flat blocks to cover the holes at $.70 each, so a 4 by 8 bed was $52.60 total, which was definitely cheaper than plastic wood. You may only need 1 level high, depending on your existing soil.

Top flat blocks are nice to sit on and easily removed to plant in holes, stick in a trellis, or set on the ground when muddy. Grew marigolds and herbs successfully in holes.

You can carry a few in your car, so just depends on how many you need and how many trips you want to make. Last year we expanded the beds to 4x16 interior so had them delivered.

We just hand leveled (well, fairly level!) as we set the blocks ourselves, slow and heavy, but you only have to do it once!
Also rolled landscape fabric around the inside edge of bed before filling with dirt, helps keep moisture in.
First year filled with bags of compost & topsoil, but last year ordered 'topmix' of mushroom compost, topsoil & sand delivered & shoveled in, mixing in a few big bags of vermiculite from Atwoods.
After initial labor it's wonderful to add a little more soil, measure & plant as I'm doing now that our icy winter has finally thawed.
I can email photos if interested.

Just figured out how to post a pic... here are 4x16' beds
{{gwi:1261890}}

Great information. Thanks!

We have a Home Depot about 2 miles away, and could borrow an SUV for the day - we could make several round trips if necessary. Lowes has 8"x8"x16" blocks for $1.60 each, and I'll have to check Home Depot prices.

I'm now thinking of one long and one square bed (our back yard gets sun in an L-shape, but I don't want to make an L-shaped bed). Several small square beds is sort of wasteful of blocks. It looks like doing 3 16" long blocks will give just over 3' in actual bed width after the width of the block itself is subtracted. 4 16" long blocks will give about 4.5' in bed width. I want to be able to do an overlapping second race if necessary, so I'm debating doing a 3'x10' (3 blocks x 8 blocks) and a 3'x4' (3 blocks by 4 blocks). A single race in that configuration would be 36 blocks, which is VERY affordable compared to other options. The existing bed is about 8" deep and things generally grew very nicely last year (even deep-rooted tomatoes). Maybe I'll start with a single race and see how things go - I can always add a second race next year to make the beds deeper.

I'm going to get some stakes and actually stake this out with twine in the next few weeks when the snow melts. That way I can be sure they're well-placed with regards to sun exposure.

ANYTHING is better than the raised bed we have now!

Sounds like you have good soil, so one high should work fine. Ours is clay/rock so had to go 2. One other reason I like 2 is its the perfect height for sitting & working, especially nice in hot oklahoma summer when moving much is difficult!
One minor problem with these concrete beds is the garden hose doesn't slide on the sharp corners, maybe investigate round block corners? Or bumpers, hose guards?
Good luck with your beds, hope we have a good vege year!

I've done a lot of research today and see that cinder blocks are dangerous. Google for yourself

I built a big cinderblock garden eons ago and I still love it. It's 24" and 32" high so no crawling, no walking on the soil. 4 foot width all around and square foot approach works fine although your soil choices may differ as this is a deep bed. Here's some pics from long ago, a blog I abandoned, no reflection on the garden lol.

http://the8catgarden.blogspot.com/2006/12/cinderblock-garden-setup.html

http://the8catgarden.blogspot.com/2006/12/overview-of-garden.html

PJ

I've worked in an herb bed that was bordered with concrete blocks. Here is coastal Virginia, the herbs and annuals we put in the holes did not thrive-- too hot. And the soil volume wasn't enough for peppers, eggplant and other heat lovers.

We lugged around a piece of lumber to sit on; the blocks were just too uncomfortable. We also found we got a lot of abrasions on our knees, knuckles, etc for contacting the rough surface.

And even tho the groundskeeper had painted the outside of the blocks, the bed was still too ugly to be in a park. It was disassembled.