Once per hour minimum, and departure times let you connect from the train from Munich to the bus without much wait.

For itineraries:
www.bahn.de
"Füssen" or "Füssen Bahnhof" is your point of departure and
"Hohenschwangau, Schwangau" is the destination (not Neuschwanstein).

It's only 3-4 km from the station, so even a taxi ride would not ruin your budget if you missed a bus.

Hi S,

You can look up the schedule Fuessen/Hohenschwangau at www.bahn.de

If you use Bahn.de to get schedules be careful how you write "Füssen". Those two little dots are important. If you just use Fussen you will not get the right place. If you don't know how to make a "ü", use "ue" (Fuessen) or "Fussen Bahnhof". The last one is technically not correct, but either one works.

To make the ü, simply copy and paste from this post:

ä Ä ö Ö ü Ü ß

(Originally, people wrote "ue", then scribbled the "e" above the "u", and eventually the "e" was reduced to two dots. Similar story like the $-sign developed from "PS" for peso.)

If necessary you can also take a taxi..there are always some waiting. More expensive I know but just so you know all the possibilities.