The Hungarian language is one of the most unique languages in Europe, and somewhat difficult to master for non-Hungarians. The majority of services/people in Budapest have a good command of English, so you should not have a problem. But perhaps you will find the following words/phrases helpful:
Jó napot kívánok = [ ˈjoː ˈnɒpot ˈkiːvaːnok] = Good day/morning
Jó estét kívánok = [ ˈjoː ˈɛʃteːt ˈkiːvaːnok] = Good evening
Köszönöm! = [ˈkøsønøm] = Thank you!
Szívesen! = [ ˈsiːvɛʃɛn] = You’re welcome!
Elnézést! = [ˈɛlneːzeːʃt] = Excuse me! (e.g., if you are trying to get out of a busy bus)
Egészségédre! = [ ˈɛɡeːʃːeːɡɛdrɛ] = Cheers!
Imádom az interferometriát! = [ˈimaːdom az ‘interferometriat] = I love interferometry!