This was a bit hard to find, but eventually we found the in-town version of Porta-Porta tonight (5 Stanley Street, 6222-7461), which is evidently run by the Changi shop's nephew. To my relief, I found it largely the same here (including the quirky decor), unlike what I had heard. The menu was largely the same too, although they had some different sets, such as the "Sea Catch" and "Mushroom Harvest" (but without that Chef's special thing). I got the former.
My starter was a set of bruschetta of fish and tomato, the second of which had just the right punch of fresh garlic (and oil) without being excessive. The fish soup in the set was also hearty yet savory. The other items were fairly similar to the other location, be it the spaghetti alle vongole, calamari & fried fish (piping hot yet light, although it was shrimp instead of fish today), and pie & tiramisu (complete in a Chinese tea cup).
One huge thing thing I like about these guys is their rich sauces, and it was evident tonight in the separate penne con gamberi we got tonight. But alas, the similarities went one too far: the pasta was a bit too soft here, although I didn't mind that too much. I'll happily come back here rather than head all the way out to Changi again. This location also makes it worthwhile for an office lunch, if I don't get my colleagues lost along the way.