Here's how you can respond, depending on your preference:
If you want hamburgers with plantains:
* Sí, por favor. (Yes, please.)
* Me encantaría. (I would love to.)
* Sí, con mucho gusto. (Yes, with pleasure.)
If you don't want hamburgers with plantains:
* No, gracias. (No, thank you.)
* Prefiero solo hamburguesas. (I'd prefer just hamburgers.)
* No, me gustaría algo diferente. (No, I'd like something different.)
If you want to know more about the plantains:
* ¿Cómo son las plantains? (What kind of plantains are they?)
* ¿Están dulces o saladas? (Are they sweet or savory?)
* ¿Cómo se preparan las plantains? (How are the plantains prepared?)
You can also express your interest in trying something new:
* Suena interesante, ¿puedo probar un poco? (Sounds interesting, can I try a little?)
* Nunca he probado hamburguesas con plátanos, me gustaría probarlo. (I've never tried hamburgers with plantains, I'd like to try it.)
Remember to be polite and respectful when responding.