Plot hole: Lucy jumps from the airliner and flies her hang-glider straight to Eduardo/El Macho's Cinco de Mayo party to find Gru. How did she know Gru would be there? He had no intention of going and only did so after he was pestered into it by the girls on the very night of the party, so he couldn't have told her himself. Shouldn't she have gone to his house instead?
Plot hole: The rocket is launched with Gru and Lucy attached to it. All of the minions are around them at El Macho's lair at this point. Considering a rocket travels at several hundred miles per hour, when they jump off it almost a minute later they should be several miles away at the very least, but three Minions appear on a boat shortly after. There is no way the three Minions could have reached Gru and Lucy all the way from the lair in that short time.
Plot hole: When Gru and Lucy are searching Eduardo's restaurant, Eduardo's pet chicken begins a fight with Gru and Lucy which involves a lot of screaming, breaking tables, the chicken battering Gru which was all very loud, yet Eduardo only finds out someone was in the restaurant as soon as he walks up to the door, despite all the noise from the fight between Gru, Lucy and the chicken.