I just did my landing the other night at the Peace Arch. I'm not sure about public transport but if you look on Google Maps i'm sure there is something that will get you close enough. If you can drive, keep your eyes open for the 'peace arch provincial park sign', basically it's the last right turn before you are committed to the border, (it's also the same exit as the duty free). Park in the peace arch park car park, walk down to the US border, tell them you are changing your status in Canada, they will send you back with a piece of paper to show you have seen them, walk back to Canada, do your landing, then walk back to your car and you are all done! It took me about 35 mins start to finish at 8pm on a weeknight.