Many of the big radio networks are buying Spanish stations or converting stations to Spanish-language formats because of the growing Hispanic population in the United States. While some stations do accept pitches in English, be aware that whether a station accepts the pitch in English can depend on who picks up the phone; you may find yourself speaking to the producer who may not speak English well, if at all.
Although Spanish-language stations may accept a pitch in English, there are a number of benefits to providing a pitch and supporting materials in Spanish. By pitching and providing background in Spanish, you are allowing the producer to hear firsthand the news as his/her audience would. Pitching in Spanish also limits the possibility of the producer/host losing the meaning of the pitch in translation.
By taking the extra step to pitching and have supporting materials in Spanish, you take control of how things are being presented, as well as demonstrate that you are sensitive to the needs of this important demographic by presenting the pitch that is easily understood.