Going with the PPL in pocket does put you in theory 10 steps forward towards your FAA CPL but it also means you go with the intent with putting less money to your potential employer. Less time in his face showing how you would fit in as one of his employees.
Plus you will have to check if a JAA PPL will allow issuance of an FAA PPL otherwise you will have to be rated on your JAA PPL in both the R22 and 300CBi so that you can act as PIC towards your FAA Commercial.
Both Slotty and WOB have really answered your chances of gaining employment with just a CFI but I'll try and expand. Firstly check out the HAI webpage for current instructors. There are 16 in Florida only 4 are CFI's the rest CFII.
Also consider that every overseas student goes with the same intent as you and every instructor will be working to get 1000 hours before his J1 visa expires. If every student roles up and flys 80 hours dual with his instructor and the rest solo, that means for every ten students, only one will get employment with the school they train at.
So you stand one in ten of a chance for a job but then only if one of the 25% leave. So now you are seeking a job elsewhere and since 1997 an FAA Commercial includes some Instrument flight instruction which you won't be able to give as you aren't a CFII which as stated above will only probably allow you to work for one of the larger organisation...... which unfortunately is the exact kind of place that you intend to do your training and what do they do...... employ from within.
Don't get me wrong I'm really not trying to convince you to not go ahead with this, just trying to let you head overseas with your eyes open and maybe some extra funds that if you don't gain employment you could call upon.
Another take is that it will take you 6 months to gain the licences..... maybe another 6 months to find a CFI job (not every school has 75% CFII's)...... leaving a year to gain 600-800 hours (you already have about 200 from your commercial). This is easily attainable.