Okay, I'll chime in here. The center is in Brindley Place, which is NOT within walking distance of New street, unless you're Paula Radcliffe. You'll need a taxi, which will probably cost you £5.
If you're driving, you can park in the NCP car park which is in Brindley Place, and about 50 meters from the center.
To get there from the M5, exit J3 onto the A456 Hagley Road. Follow it all the way until you get to the Ivy Bush pub on your left (about 4 miles, in the middle of a row of shops at a set of traffic lights). Turn left at the lights, go straight to the end of the road. You'll come to a roundabout. Take the second exit (Ladywood Middleway) and go to the end of that dual carriageway. You'll come to another roundabout, go right. Immediately get in the right hand lane and stay there. You'll come to a set of traffic lights, you'll be in the filter lane to turn right. Turn right when they go green (doh). Now skip down.
To get there from the M6, take J6 to City Center (Aston Expressway). This is a super fun road that's just like being on a rollercoaster - a motorway with no crash barriers. Seriously. Follow it all the way to the end, you'll eventually go under an underpass then onto the FIRST flyover. Go over the FIRST flyover. You'll go into a tunnel - GET IN THE LEFT HAND LANE. As soon as you come out the other side of the tunnel, a road will join on your left - get onto it - DO NOT GO INTO THE SECOND TUNNEL (This will make sense when you're driving it). Drive up the steep hill to the traffic lights. Cross the traffic lights, drive to the end, the road will curve to the left and you'll come to a roundabout type thing in an underpass. Get into the RIGHT HAND LANE IMMEDIATELY. Follow the road round in a circle - you'll end up on the opposite side of this rounabout thing. Another 2 lanes will join on your LEFT as you go under a footbridge, GET IN the LEFT hand lane. Go straight down this road, stay on the left and you'll go past a roundabout with a BMW garage on your right. At the next traffic lights, turn left. Skip down!
At this point you're in the same place. Follow this:
Follow the road round a big bend. You'll come to another roundabout with the NIA car park in front of you, go right here. You'll drive past the car park (on your left) and round a 90 degree left hand bend. Drive straight up to the next roundabout and go left (the City Inn will be on your left). When you go left here you'll get onto some cobbled street thing, you'll see the NCP car park in front of you. Before you drive into the car park, look to your right. That's Brindley Place - at the end is a Bank restaurant and the Sealife Center.
If you get lost, don't blame me