Do you want to speak (in) your language? Do you want to hold this conversation in your language?
Would you appreciate to speak (in) your language? Would you like to hold this conversation in your language?
[Língua = language (idioma)]
If I'm asking someone whether they speak that language, I'd prefer "Do you speak English?" If I were telling or instructing children, for example, I'd use "Speak in English".
There isn't much difference in meaning between "speak English" and "speak in English" from a practical point of view. There's actually very little difference, and it's very subtle.
To speak [language] is a non-contrastive do speaking using [language]. This form is usually used with knowing and learning.
Ex: I [know / learned] how to speak English.
To speak in [language] is a contrastive communicate using this method rather than another. This form is used more often when there is a choice. The following examples uses speak in as conduct the meeting in.
In my opinion, speak English also has a sarcastic meaning. When someone is speaking English but is very unclear, perhaps because they are using technical or legal terms, you can say "speak English" to mean "say that more clearly." It would be very odd to say "speak in English" for this purpose.
I hope that makes sense.
REFERENCES: (1) HURFORD, James R et al.Semantics - A Course Book. Cambridge University Press. 2007. (2) PEREGRIN, Jaroslav. Meaning: The Dynamic Turn. Current Research in the Semantics/Pragmatics Interface. London: Elsevier. 2003. (3) HARPER, Douglas. Online Etimology Dictionary. 2010.