Technically there is no future 'tense' in English grammatically. That is, there are no morphemes that signal or create future. Many grammarians will say then that with regards to tense, English has two - past and present.
Of course, the future exists, and so we need to be able to talk about it, however we do this using adverbials and auxiliaries, not by changing the verb as languages which do have future tense would.
Examples of future tense expressed in various ways:
"Tomorrow, I leave for London." - Future is indicated by adverbial tomorrow.
"I will leave for London." - Future is indicated by the auxiliary will.
"I am going to leave for London." Future is indicate by auxiliary and progressive aspect.
As for your example:
"My friends and me will go/are going to Spain in Summer 2010." - either 'will go' or 'are going' is correct.
I should point out that it should be 'My friends and I', and also that summer is not capitalised. Thus:
"My friends and I will go/are going to Spain in summer 2010."
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