Unfortunately I am all too familiar with this crossing!

If without a car you have 2 options:
1) take a cab across as you have already said
2) walk across the bridge. I have done this many times - its about 5 min walk to span the bridge and another 10 or so to casino (however you can grab a cab once you get thru customs on US side and cab it to casino) Its a great view of the falls from the bridge but if you choose this route your comfort will depend on how much stuff you're lugging around.
Let me know if any other questions...like I said - I've done this crossing a lot. I live in Toronto
CHeers
Mike