Try to avoid Budapest for a few days now, the public transportation system is down due to a strike at "BKV". Subways and some trams provide a limited service, but this could change any minute.
If you come anyway, prepare to take a taxi (always call cabs by phone, avoid hailing them on the street.)
The whole thing should be over by next week.
Does not happen often, definitely more rare than in France for example :-)