This is the only absolute rule with regards the higher level members in the guild. Absolutely NO BOOSTS will be offered! You gain nothing from having a high level player running with you and experience gained from running with the correct level group in any instance is invaluable. It will stand you in good stead when you hit OL instances and you won't look like a noob in front of other players in a PUG!
Just bear in mind that we all want to get to 70 and once there the game starts for real. (I speak from experience having a few level 70 chars myself). I personally do a lot of solo questing and avoid the low level instances as the rewards are negligable and change in a few levels anyway! I only really start to concern myself with gear when I hit OL as there you really need cracking gear to survive.
Thanks for understanding and happy gaming