Hello there nakayama_kun and all !! I don't think I've ever posted here because after once checking it out, I noticed that everyone answers well enough that there is really no need for me to add anything.
Anyway, just to add my thoughts here.
Glenn got it right; 'in about two weeks' would be most correct because 'about' modifies 'two weeks'. However the orally spoken sentence could be correct if we assume it were more of a phrasal verb-like thing. This would be 'see you about in two weeks' which would be the same as 'see you around in two weeks.' That understanding would basically equal the 2ツ週ナ?テ版津」窶堙俄?ーテッ窶堋「窶堙懌?堋オ窶堙・窶堋、, without any need for 窶堋セ窶堋「窶堋ス窶堋「.
At the same time, it could be said that 'see you about in two weeks' could be allowable as far as actual usage goes--again, in oral communication. The speaker would be thinking as they were speaking and it may come out as, 'see you,....uh...about in two weeks?' as the actual time is uncertain and the statement may have a bit of rise at the end, as though asking for verification of that time period.