Hi desertdance,
Blackberries are easy to grow when you know how to .
I wouldn't use mulch on blackberries .
The reason is easy to understand : Blackberry's cycle if done in two years ; first year the cane grows, second year it fruits and dies , so you have to let new canes come out of the dirt and espalier them - if you cut the shoots, then no or less fruit next year.
I wouldn't keep those wild bb, because they are too close to the dirt - and so sorry to tell but you need to know- and so foxes ... and dogs tend to "put the leg up" on them.
Here they say to never harvest anything under the height of 50 cm or even a meter is better - but everyone does as they feel comfortable with ...
I have 3 bb, and unknown with thorn, an unknown thornless, and a thornless "Jumbo" BB .
The big problem with bb are the stains on clothes and tongue/teeth so I tested Muroisiers/loganberry and those have my preference now - just suggesting .
The other problem with bb is with rainy weather when getting ripe - they'll then get really sour.
As for care, they need water to grow well - an 11L watering can per week and some manure/fertilizer and they are happy .