I got this from the webpage of the emabssy of Hungary in Los Angeles:
losangeles.mfa.gov.hu
Visa Exemptions
Visa free entry Citizens of the EU/EEA member states and of the following countries may travel to Hungary without a visa and may stay there for a maximum period of 90 days during the 6 months from the date of the first entry (if the conditions required for staying are met): Albania, Andorra, Antigua and Barbuda, Argentina, Australia, Bahamas, Barbados, Bosnia and Herzegovina, Brazil, Brunei Darussalam, Canada, Chile, Costa Rica, Croatia, El Salvador, Macedonia, Guatemala, Holy See, Honduras, Hong Kong (the exemption applies only to holders of a “Hong Kong Special Administrative Region”), Israel, Japan, Malaysia, Macao (he exemption applies only to holders of a “Regio Administrativa Especial de Macau” passport), Mauritius, Mexico, Monaco, Montenegro, New Zealand, Nicaragua, Panama, Paraguay, San Marino, Seychelles, Serbia, Singapore, South Korea, United States of America, Uruguay, Venezuela.
ATTENTION! Nationals of third countries, who are exempt from holding a visa when crossing the external borders, can only enter the Schengen area with a passport which
(1) shall have been issued in the prevous 10 years and
(2) its validity shall extend at least three months after the intended date of departure from the territory of the member States or, in the case of several visits, after the last intended date of departure from the territory of the Member States.
Stateless persons and recognized refugees holders of a Travel Document issued by one of the above mentioned states, can enter without a visa (in case of US Travel Documents: if the annotation: "refugee" or "stateless" figures in the travel document it can be used for travel without a visa. A visa is needed on the "simple" travel document without these annotations). Stateless persons and refugees residing in a Member State, having a travel document issued by the Member State concerned are entitled for a visa free entry. Member State means: “old” and “new” Schengen Member States, Cyprus, Romania and Bulgaria. In possession of a valid D+C visa issued by one of the Schengen states, within the first three month of the validity of the visa, the holder is entitled for a visa free entry. In possession of a D visa, the holder may only transit through Hungary to the issuing country without visa. In possession of a valid residence permit and other documents listed in Annex 4 of the Common Consular Instructions, foreigners have the right for a visa free circulation within the Schengen Area not exceed 3 months in any 6 months. Holders of United Nations laisser-passez may enter without a visa.