Did Saganbo train or get stronger within those 2 and a half months, since they left Namek and arrived on Earth?
Logically, Saganbo, receiving energy from Moro on Namek, strengthened him a lot, but not to the level of reaching Moro's power at that time. That version of Moro was inferior to Goku/Vegeta PSSJB (before training).
Then upon arriving on Earth, Saganbo (before receiving his 1st boost from Moro on Earth) was confident of defeating the Warriors who had defeated OG73I (Moro).
It's also possible, as when Moro and Saganbo find out that Vegeta had defeated Yuzun, it makes Saganbo shocked, as he calls Monster Yuzun invincible. Saganbo, knowing Moro's absorption technique, means that Saganbo knew an important % of Goku/Vegeta PSSJB's powers. Also, after learning that Vegeta had killed Yuzun, it made Moro decide to get as strong as possible in the time he had left to go to Earth.
Do you mean to say that Saganbo got stronger within those 2 and a half months?