At this point if you believe Oswald didn't go to to Mexico City then, gosh, you really have a bad case of conspiracy fever. Take two aspirins and get a nap. No, make that four aspirins.
If you think you know everything there is to know about Oswald's visit to Mexico City, you're not being honest. It's impossible. There's far too much conflicting information and not enough hard evidence on what he did, what places he visited, who traveled with him, etc.
I don't know what to believe about Mexico City and Oswald. It's very plausible that he was in fact there but I'm stuck on these facts:
- No photographic evidence.
- Possible impersonation attempt in phone calls to the Soviet embassy (the Russian language interpreters weren't sure if it was the real Oswald).
- Inconsistencies with the Sylvia Duran-Oswald timeline.
- The Silvia Odio detour.
- Witnesses gave descriptions of Oswald that didn't fit his physical description which indicates an in-person impersonator.
- There was a huge US intelligence coverup relating to Oswald's visit to Mexico City.
- No souvenirs. Not even a postcard from Mexico City.
Furthermore, if it was the real Oswald, the whole trip to Mexico City on a weekend to get a Visa makes no sense if that was his true intent.
If someone impersonated Oswald, perhaps it was part of the CIA/FBI efforts in 1963 to smear the Fair Play For Cuba Committee. COINTELPRO/CHAOS didn't officially begin until the late-60s but there were similar attempts to sabotage Leftist organizations in the early-60s. Oswald had no friends or associates who were communists or marxists. His persona via the letters to Leftwing organizations and public appearances in New Orleans has the appearance of being manufactured. Outside of his public persona at that time, there's no evidence that he was a devoted communist.
The more sinister possible reason to impersonate Oswald in Mexico City two months before JFK's assassination was to connect JFK's assassin to the Soviets and Cubans. No one could've predicted in advance that LBJ would suppress any potential ties between Oswald and a communist conspiracy in order to avoid war with Cuba or the USSR.