MegaMewtwo - Oh, yea, but their encounter rates are fairly low I think. Forgot about that. A LARGE space would be route 222 (I think) outside the resort on the way to SunyWhatever Town. That field is huge. Chatots and Mimes reside there, but I can't remember the Radar-only poke.
Kamikaen - As for the caves part, I guess I failed to mention it technically, but the whole thing revolves around grass, so I figured people would catch on, which you did. Also this is all from experience, non is from the game's coding. In general, if you just avoid the bad ones you'll be okay. However, over the long run you'll find that being more conservative later in chains pays huge dividends, because you're entering the surest of patches. Also I would strongly advise that you spore, trap, or Quick Ball Abras. If you miss with Hypnosis, which is pretty likely, it's all over.