I had my first experience of Poland last October and loved it. We had 3 days in Krakow and 3 days in Wroclaw, and with my missis being ill for alot of it and not wanting to do too much, I managed to do quite a bit of exploring.
Wroclaw is a great little city with plenty to see, and it's pretty much all within walking distance from the main square, or if you're not feeling quite so energetic, very easy to use the trams.
If you want to get around Wroclaw on the cheap you can get a 24 hour local transport ticket from the tram stops for 11zl (£2.20) or 20zl for 48 hours. It's also valid on the suburban trains out as far as the trams go, however, you need to validate the ticket on a tram before you can use it on a train. I didn't do this so when I got the train out to Brochow (large loco depot and freight yard) it cost me another 4zl (£0.80). On the way back the train was so crowded the 2 guards couldn't get through anyway so I wasn't too bothered that I'd had to pay an extra 80p!
Wroclaw Brochow is the place to go if you want to see some Polish locos. You have to get there by train from Wroclaw Glowny but it takes less than 10 minutes. An hour or 2 should be enough to do a thorough walk around the depot, maybe longer if it's good weather and you want to hang around for some passing freight.
The station is very small and an absolute dive! Local trains and ICs pass through the 2 platforms and there are 9 freight lines in a holding yard between the station and the depot. You can just walk off the north end of the plaforms and across the tracks to get to the depot and main yard, they're not visible from the station but there's plenty of routes through the trees and nobody seemed bothered with me walking around taking photos. Once you're across the tracks it's a 5 mintue walk to the depot. Just look on Google Earth or maps etc, it's pretty easy to work out.
I went down there twice on my 3 days there, both times I got about 50 locos around the depot, some of which are withdrawn. On the 2nd visit I even managed a walk right through the main shed, another 10 or 12 locos inside here too.
On the whole I found Poland very welcoming, the people were great, the food was lovely, and even better, nobody seemed bothered at all when you just wander off station platforms or into depots with a camera and start snapping away (obviously with a high viz vest).
A last recommendation. If you've had enough of the local cuisine and live music is your thing, opposite the medieval town hall on Wroclaw square there's a restaurant called Whiskey in the Jar. It looks like an imitation Hard Rock Cafe, but the food is really good and there was a fantastic band playing in there. I think the whole night including copious amounts of food & beer cost less than £25.
Enjoy your trip, I'll be back over there as soon as I can.