The easiest is to take a taxi which should cost around HUF 6800 (about $25). It is customary to give a tip, about 500 HUF, but at most 10%. When arriving to the airport, do NOT take a taxi from people offering rides in the arrival area. Simply walk outside and go to the official taxi booth (called Főtaxi) and tell them you are going to Hotel Gellért and they will tell you the number of the taxi that will pick you up and give you a sheet with the info of the taxi and the address you requested.
If you intend to use public transport from the airport you have to take bus number 200E to the M3 metro's terminus at Kőbánya-Kispest. There you switch to the blue M3 metro line to Kálvin tér, where you can switch to metro line M4 green to Gellért tér (2nd stop) where the Hotel is situated. (You have to buy two single tickets (350 HUF each) in advance, one for the bus and one for the metro. You should be able to get a ticket on the bus for HUF450). There should be ticket machines at bigger bus stops which also have an English menu, so you should be able to buy your tickets there. For those intending to regularly use public transport the weekly ticket might be a good choice (HUF 4950). For more description of public transport see http://www.bkk.hu/en/main-page/news/.
If you are arriving by train then you can take any official taxi around the stations (with a taxi sign on the top) from the official taxi stops. Again do NOT accept a solicited ride, but look for the official stands.
If you are arriving to the East Railway Station (Keleti pu.) you can take the green metro line M4 and get off at Gellért square (one single ticket, 350 HUF).
If you are arriving to the South Railway Station (Déli pu.) you can take tram 56A and get off at Gellért square (one single ticket, 350 HUF).
If you are arriving to the West Railway Station (Nyugati pu.) you have to take the metro to Kálvin square (tér), where you switch to metro M4 (one single tickets, 350 HUF).
Please follow the map below for a 15 min walk. Csaba will be waiting in the Gellert lobby Monday morning and lead a group of people leaving at 9:15AM. The conference itself will be in Room 0.83 at the Eotvos University's Natural Sciences College (ELTE TTK) Lagymanyos Campus Building 1/A.
View from Gellert to Physics Building in a larger map
For those already in Budapest Sunday afternoon (July 2), Csaba will lead a tour of the Buda castle. Check-in time at Gellert is 2pm, so we will meet with those interested at 2:30pm in the Gellert lobby and go from there.
In case you have a last minute emergency you can call Csaba's cell number in Hungary at +36 30 963 2930.