I thought I should share some pictures of my Kei apple, hybrid/Tropical apricot is a natural occurring hybrid from Florida, developed in 1953 from a kitembilla, (Dovyalis hebecarpa) and Abyssinian gooseberry (Dovyalis abyssinica).

http://www.fruitipedia.com/tropical_apricot.htm

I chose a very thorny version for fencing and a nearly thorn less one for fruit production.  Here a a picture of what to expect if you plant them and leave them for a year in ground.  They require pruning to get a thick, dense hedge.  

     
 
Roses will work nice as well.  

 


Good luck 

Blue, some prickly pear are extremely thorny and easy to propagate, though maybe not fast enough to get going for your needs.  I have one pretty good candidate but can probably only spare 5-6 pads.  Good luck.

Blue

    Here's my take. Your good with dogs. You have fence height restrictions. All you need is  a shorter dog. Train a Teckel or two or three and put some signs up. For the fence, three feet will  work for the dogs, but you can double it for the two-leggers and still be within restrictions.

I don't think any plant here could come close to this one " Flying Dragon " I had a few of these in my yard and had to get rid of them all but one of course this plant is so brutal that when you get stuck with one of the thorns the area is in pain a half for a hour after these thorns are so tough that when I used to trim them if you stepped on a thorn with work boots it would go right through the sole I read somewhere that they use them in Japan around there homes for security but like Frank said they are dangerous I had small kids and I was afraid they would get there eye poked out They use the the root stock from this plant for Meyer lemons , Limes and other citrus , Super cold hardy as mine is in Connecticut grows like a weed and bears lots of fruit 

     

   Cindy,  from one newbie to another, welcome!

   The Kei Apple are native to the southern tip of Africa.   They really surprised me at how long they took to germinate...  I thought at first that the seeds weren't viable.

   I have quite a few plants growing now...   if you'll PM your shipping address,  I'll get some sent your way.

           Smiles,

                   Blue

Welcome, Cindy!! Great forum! You'll be informed and enthused here! Not to mention some great laughs!

   You're quite welcome, Cindy.

   Yes,  they are really a bright green aren't they?!   Even though they are soft and supple now, just keep reminding yourself not to plant them anywhere that you wouldn't want concertina wire:  LOL!!

   
      

Blue if your going to use that fence don't forget a Guard Tower it makes it just that much nicer 

 

  What was I thinking Dave?!!!    

   That's the look that I should have gone for...  LOL!!    

   It would have given these crop thieves a preview of coming attractions!    Blue 

Welcome to the forum.
I guess you would need both male and female to get a crop. It says that you need about three to five years to get fruit. Is the fruit worth waiting for (Taste Wise).
I like thorny plants especially if they make nice fruit. In my yard, I have 10 varieties of jujube trees which are very thorny, but since I like the fruit,
I don't mind the thorns.

Yes, Sas...   both are indeed needed, but not hard to attain with the routine mix of seedlings.   I've read that the fruit are usually eaten with a sprinkling of sugar as they are a little on the sour side...  no personal experience here;  Sid  (FiggySid1) grows them both for fruit and as security, so they must offer something worth eating.

We are working hard to keep the Med fly from getting a foothold in Northern Calif...  so I'm going with a single-sex planting.  These Kei Apples are so productive that after the Israelis had planted them for security around their farms, they became a huge hatchery for the M/F, and had to all be torn back out. 

I don't know about the non hybrid one, but the one I have is somewhat sour with a apricot aftertaste. I only use the fruit for making juice (think lemonade).

The recipe I use is

1 gallon of water
2 cups sugar
100 tropical apricots (they are small) (quarter size)
Chilled in the refrigerator or poured over ice.

It's one of the best tasting juices 2nd only to Naranjilla, which Is also a fast growing thorny plant.

It should be interesting to know if anyone ever succeeded in making it fruit in a container? According to Purdue University "enduring brief drops in temperature to 20º F (-6.67º C) but descents to 16º F (-8.80º C) have been lethal in this state and in California" I am to presume that temperature in your area never went down to 16º F.