I'm another one - this used to work just fine for me when I got my 4S, I could say "What time is it" and Siri would tell me. For the last week or so if I ask I know get "I'm sorry, I don't know what time it is in xxxx road". Likewise, if I ask what the weather is, rather than tell me the local weather it will say "The weather for England is..."
However, I've got another glitch which I think could be related. When I've used location services with any of my iPhones, including my 4S when I got it, especially indoors where the GPS signal is poor or there is none, it's quickly got a fix on my approximate correct location presumably using WiFi and mobile phone mast data, and then within a short while it has refined this once it's got a GPS fix.
My 4S started doing this when I first got it, but now when I try it always places me about 30 miles to the east of my correct location until it eventually manages to get a GPS fix after a couple of minutes. I'm guessing it doesn't actually think this is where I am, its just that the only non-GPS fix it can get is so vague that it knows it's somewhere 'about' there, give or take 30 miles. And I think this might explain the Siri glitch; when Siri can't get a reasonably accurate location fix, it only gives generic weather and throws a wobbly not knowing which time zone you are in to report the weather. I'm not sure why location services are this innacurate on the 4S, like I say my previous iPhones have managed to get it down to about 250m without any GPS assistance and my two daughters' iPod Touches both manage the same on WiFi alone.