This is grammaticaly correct, but it sounds impolite if you say it to others. Although it is the present tense, it is also the imperative so in Spanish we normally use the conditional tense for asking for things. Example: Yo querría ( I would like ) Yo necesitaría ( I would need ) Yo desearía ( I would wish) If you are not used to the conditional tense in Spanish, I would use "por favor" Example: "por favor, un café" / " quiero un café, por favor"