In the second book Dodgson concocts a plan to steal T-Rex eggs from the nest.
How could anyone say he isn’t smart?
If the book, though different, is canon addition to the movie, then yes, Nedrys plan was to steal the embryos, drive the jeep through the jungle, meet a go-between on the boat (since this was a supply boat and not the main dock, this was possible) hand over the thermos and be back in 15 minutes, claiming he was at the vending machine. He would then have restored the computer and phones, erased his little program, and nobody would have known.
The scientists would probably not have noticed one test tube for each species missing until later, at least, that’s what Nedry thought. Maybe the scientists did track the embryoes more closely.
Also, in defence of Nedry, this didn’t seem to be typical rain forest, or a typical rain forest shower - short, at noon. Rather, it was a big-ass rainstorm with thunder and huge rainfall. Judging by the weather before and afterwards, the “daily shower at noon” tropical climate doesn’t apply to this island. And frankly, that makes sense if you want to bring tourists there like Hammond planned - people won’t like regular showers or hot and humid weather, they want dry, moderatly hot weather. So somehow Hammond picked an island with more California-like weather than tropical rainforest weather.