Will it be easy to find a taxi to go up the hill to the Castle in Prague? My mother has difficulty walking but we hate to miss it.

If her difficulties in walking are not too severe, you can get there by tram. See: http://www.myczechrepublic.com/pragu...ue_castle.html

There are cabs everywhere and they will all be happy to take you to the Castle. Since my SIL has walking problems we took the tram up and then walked down through the Castle and the Golden Lane. And it was easy to get a cab at the bottom too to get back to our old town hotel.

Except that cabs are a major rip off in Prague. AVOID THEM AT ALL COSTS..unless your hotel has called it and given you a taxi voucher!! Take the tram. It takes you right up there. You can then take the tram back down again. Its easy and comes every few minutes. Your hotel can tell you what number tram to take.

Cabs are pretty cheap in Prague, I wouldn't go through the hassle of the tram if your mother has difficulty walking, that's for sure (and what about the walk from the stop to the castle? It's a ways). If you are staying in any moderate or nicer hotel, they should have a reputable driver they work with who can do that for you.

It depends on how bad is your mother's difficulty in walking but if it's really bad, from the tram stop far behind the castle (22 & 23 stop there) to the castle's gate is not such a quick walk especially for those with walking difficulties. About 800 meters (a half a mile) according to the map I have. This way at least you can avoid the uphill walk on Nerudova street though. Tram stop (Pohorelec ?) to the castle is slightly downhill.

You don't need to be a paranoia about Prague taxis. They are notorius but getting better lately thanks to the city's new policy, I hear. If not, at least two taxi companies have been reliable. AAA & the other, I forget the name.

How poorly does she walk? There are cobblestones galore in there. As I remember, the Golden Lane is very uneven. Perhaps you should Google some photos of the castle grounds to show her, so she can judge for herself whether she's up to the task.
If she can handle it, I'd recommend the tram. It couldn't have taken more than 5 minutes from river edge to the castle bus stop, then about 300' down a gradual slope thru the castle gate.

You can take a taxi to Hradcanske Namesti (castle square) & walk right in. There aren't many cobblestones right there at the main gate, if any. St Vitus will be a close walk & then you can turn around & take a cab back. It will not be that expensive. Use AAA or even a private driver who could give you a tour, etc. I would not attempt to walk down the hill, as others have suggested. It is a long way down, and the pavement is uneven. You can stand at the top of the hill at the square & get great views. Then taxi it back down.