Well, what city is she going to? Maybe someone can help with location specific advice. For instance, if she's going to NYC or DC I'm sure someone can help her with sites (hopstop.com is good) for figuring out point A to point B without a taxi.
Buses do not have seatbelts. They have size going for them. Are they the safest? I'm not sure. Certainly between a taxi with that POS seat or a bus I'd choose the bus. And I have chosen the bus. And I will choose the bus.
We have traveled with Piper a LOT. Big cities and small towns. If it's small enough we rent a car, or I've installed her carseat in taxis and shuttles. You gave great advice, make sure she knows the seat before she goes. In cities that are fairly big but small enough not to have a huge public transportation system I use my feet quite a bit. Seattle is a great example of that. Piper and I have walked all over the city. North to Belltown, south through downtown, west to the water, and east to more water. Or depending on where we were going I'd look up the bus routes and take us on the bus. Piper enjoys the bus. Even when out in Seattle when we went out of the city and to a suburb we took a bus. It's a great way to see a bunch of areas you wouldn't see on your own.
In New Orleans the last time we were there (pre-Katrina) I set out on foot and after a mile or a mile and a half when I couldn't find what we were looking for I got us on the cable car and we took it back down to our area. I've walked over a good chunk of New Orleans. Again, a great way to get to know a city.
DC has my favorite subway system. I've flown into DC, rented a car just so I could get from the airport to the furthest subway stop. Park in a park n ride and get on and go downtown that way. Many times I've simply taken my own car. I've driven to DC, I've driven to NYC, I've driven to southern Florida. That freed me up to park in or near the city and then take public transportation from there. Or walk. In NYC I take the subway, second to that I take my feet, and third to that (especially going from west to east and back to west again) I take buses. Even in China we were frequent bus riders and subway takers. NYC taxis are tame compared to them.
Rather than a terrible carseat, maybe she could invest in a good stroller or baby carrier (I'm nervous about pushing a baby in a stroller in front of me in cities. There are crazies on the roads!). Then get a bus or subway map and just hoof the rest of it. If it's so far that there aren't buses or it's too far or hard to walk, then renting a car is an option. Maybe having someone give her a ride? Borrowing a SS1 for the trip?
And just because she's traveling doesn't mean he should be unsafe. How are they getting to this place? Flying? He should have a seat and his carseat on the plane (RFing) anyway. It's a PITFA to travel with a carseat like that without a car on the other side. I've had to leave our carseat in our hotel room while we walked inbetween needing it in taxis to and from the airport. I've brought it random places, like Tiffany.
Where is she going and how is she getting there? What is she planning on doing? Does she have access maybe to a SS1 and a stroller for it? How about a baby sling or a backpack?
She sounds really open to suggestions and advice. Can she come here and we can talk to her directly?
Wendy