Turbo told me his answer before he posted it on here yes, to be precise he got it before I even gave my second clue, all he knew was East Island City when he told me his correct answer and I told him to give the other guys a chance. There's nothing to be gained by me giving him more clues, that would frankly be a pathetic thing to do and I'm a little insulted that you'd even consider I'd do that. I told him to go for it now as nobody else seemed to be interested plus he rightfully and correctly knew the answer I was looking for before anyone else (or at least anyone else posted) therefore he rightfully deserves the next go.
The sign is located on Harrison St. on the north side of the road just above another insurance sign (which was supposed to throw people off) and it's about the size of 2-3 windows combined. In free mode there's also a health spawn very close by.
Unlike other questions I decided for this one it not be one which could not be googled and easily answered via wikia style websites and such. So I drove myself and looked for something a little tricky that I could drip feed clues to and that was the first thing I found that could either be found directly or could be guessed with my clues, old/young was the age part, and broker is a term often coupled with insurance companies which was a clue I would later use before giving out the street name. TL actually spoiled my fun a bit when he got it right after my first clue, but I guess he has the time to spare to go search for the sign, chances are he drove onto the island via the bridge (which leads on to Harrison St.) and then looked for the sign on that road itself.
I mean it's not a popularity contest, there's no prize for being correct, it's a trivia thread, who gives a toss who get's it right or indeed wrong for that matter. So long as it's something which makes people think or learn something new, even if it's not important, it's all good.