This is all fine, but at the end of the day he really doesn't have a say if, indeed, the UK leaves the EU. It is ovbviously going to be years (at least two, it has to be more) before it happens (if it does) and nobody can predict what will happen. The Spanish Foreign Minister, on 24th June, stated that they would apply for joint sovereignity over Gibraltar! The local mayor doesn't really have a say over that. That would obviously affect alot of people living and working in the Manilva area - as we all know alot work in Gibraltar. We also all know that alot live under the radar and don't pay Spanish taxes! I, for one, don't mind if they are weasled out - they live in Spain and should abide by the law of that country. That aside, those who live within the law may have to go through a few hoops to clarify their legal status, but that won't be a problem if they are legal.
So, at the end of the day, should the UK leave the EU, it will probably have an affect on those non-resident owners and the inheritance tax issues, but shouldn't really affect those who are legal anyway. So, his message of 'welcome and don't worry' really isn't relevant in all honesty. :)