The conference will be held in the romantic 19th century building Gólyavár of Eötvös University, in the very center of Budapest.
Street address is 1088. Budapest, Múzeum krt. 4. Here is the map of the location.
Excerpts from Rényi Institute's Contact & Directions page
If you don't have a lot of luggage, the cheapest (and sometimes fastest) way is to use the regular (blue) bus service that for the price of a regular ticket (320 HUF) takes you to the end station of underground (Metro) line No 3. On this bus you can also buy a ticket from the driver. Bus No 200 stops at both terminals roughly every 12-15 minutes. Bus No 93 stops at Terminal 1 only (see schedule). Buses are available till after midnight, but keep in mind that the last underground train leaves at 23:10 (there are night buses afterwards).
There is a shuttle service called Airport Minibus, which costs 2990 HUF per person. You can also buy a return ticket for 4990 HUF per person. The Minibus shuttle picks you up together with 4-5 other passengers and takes you to the address you give. You may buy your minibus ticket at the counter in the arrival hall (ATM's and exchange bureaus are available at the airport). You may also buy a round trip ticket (about 3900 HUF). Your return trip should be ordered by phone 1 or 2 days before leaving. (phone #: 296-8555). For years this service was the best one, but recently the quality declined (they have less cars, etc.) If you see many people waiting, it is better to take a taxi or a bus.
The taxis you see when walking out of the airport, Zóna Taxi work with a fixed transfer price (4100-4200 HUF). The price for the way back is even less: 3000-3500 HUF. Most of the other taxi companies also have fixed airport rates, and can be ordered in advance. You can find a list of the companies here
Arriving to Budapest by train
Trains from abroad usually arrive at Keleti railway station, from where you can take underground line No. 2 and several buses. If you arrive late at night it is better to take a taxi (see above).
In Budapest, there is a great variety of public transport: underground (metro), buses, trams, even trolleys. For more information on schedules or night services see the page of BKV Rt. (Budapest Transport Ltd.)
Prices are constantly rising; as of July 2010 price of a single
for any form of transport for one journey of arbitrary length) is 320F.
You can buy blocks of 10 or 20 tickets which are somewhat cheaper than buying
just single tickets.
There are also monthly passes but they are worth buying only for
those staying for at least a month and are regularly using public transport.
You can read more about different kinds of tickets and passes here.
In general, when taking a taxi while in Budapest it is better to take one belonging to a taxi company. Otherwise you should inquire about the fare in advance in order to diminish the risk of an unpleasant surprise. (Also if it's possible, call a taxi by phone instead of flagging one - it's cheaper)