The Spanish laws on MJ are centred arround trafficking. This means that on your own private property you can do what the hell you want. A reason to previously be busted would have been the police having evidence of trafficking from where you are growing, or you are growing on a commercial basis (trafficking means you take the weed off your private property - and it can be as little as a gram). It was quite a grey area. This also appllies to the production of seeds. which is totally legal in Spain....hence why we have a company there. However this year from the 1st of July a law has been passed that allows you to grow on your property with the main rule element being that your grow is not visible to neighbours (and I would assume smells etc also count). This is similar to The Netherlands but in The Netherlands they restrict you to 5 plants per household. If your neighbours complain in NL the police can take your plants away (even if 5 or below).
You cannot smoke in public in Spain, you have medical clubs (associations) that you can become a member of and you can also grow for your association. Again, there has been a lot of people caught/busted by dubious police coming out of Clubs with their own personal weed. So its definitely moving in the right direction in Spain (one thing they seem to have got right!)