Hi again, craigh. Are we enjoying the season? Oh yeah!
Good question. I'd say the answer depends on your roster size and how deep your league is. If you have enough room on the bench, by all means take a flyer on a guy like Jones or Pena. If you'd have to drop a solid player, sit tight for a bit.
I think Jones is a nice sleeper, but warnings of tougher times to come are valid. Jones hits well against righties, but his value this season will depend on whether he can touch lefties or not. If you can make daily lineup changes and start him only against righties, he should do pretty well for you.
I'm not so sure about Pena. He hasn't gotten as much press as some other rookies, but he has a world of talent. I think he'll have some pretty rough slumps though, and his value will depend on how much his playing time drops as a result of those dry spells.
I'm not sure anyone can predict the next Pujols (predicting Ichiro was much easier), but don't let the hype surrounding Blalock, Burroughs and Ensberg let you forget about Eric Hinske. I think he'll quietly put up some nice numbers. Bobby Hill might still be solid if he's called up fairly soon, too, but that's a substantial if.