Whats agood place for 55-70 attack training?

Giant Spiders on the third floor of the stronghold. Bring good food.

Here is a very good training guide.

http://runescape.wikia.com/wiki/Pay-to-play_Melee_training

If you want lies, cheat and deceit, go to the RS wiki. You should do experiments.

Do "the creature of Fenkenstrain" and then train in what I call "experiment cavern" it's a small cave with level 25 experiments in it, they have 100hp with 4exp per damage, 100 X 4 = 400exp per experiment

you find the cave during the quest

Hill giants.

Fight experiments or rock crabs.

Slayer

Like Shadow_Ninja14 said, do Creature of Fenkenstrain to kill experiments. Another way is to start Fremmennik Isles and kill Yaks on Neitiznot or go kill rock crabs in Relleka.

You could kill white knights thats what i did from lvl 60cb to lvl 70cb with 60 atk 60 str 52 def 54 range and 43 mage.

You could also try looking at the runehq.com and use the calculators and see how many of each monster you need to kill.