2nd Batch, Quick Question

So I just finished brewing batch #2 (pumpkin ale) and the OG was 1.055 so I attached a blow-off just to be safe even though my primary fermentor is a 6.5 gal. bucket. I'm just curious, how will I know when there is activity since there is no airlock to bubble? and also, when will it be okay to remove the blow-off and attach the airlock since the blow-off is taking up needed space in my closet?

Recipe was:
6lbs amber malt extract (3.3 lbs LME, remainder DME)
1/2 lb Wheat Malt
1/2 lb Munich Malt

1oz Perle for 60 min
1oz Hallertau for 5 min

steeped gains for 15 min at 160deg.

added 1 lb pumpkin to 1/2 gal water and heated to 160deg for 7 min and put in fermentor before adding wort and topping off with spring water.

Dog,

You'll know when fermentation begins because the end of the blow off tube that isn't in the top of your carboy should be submersed in a vessel containing water. Use a pot, pan, tin, margarine container, etc. Fill it with enough water that the end of the tube is fully underwater. When bubbles start bubbling out, you've got some fermentation going on.

I also meant to ask about getting hop pellets in the fermentor as I was unable to strain it out, any recommendations on a strainer to purchase for the future? Ditto hot and cold breaks although I kept some of that out.

I just picked up a big ass kitchen strainer from Target and a big ass funnel from my LHBS. They work like together like gangbusters!

Are the strainer openings small enough to stop hop pellets?

Yes,

The strainer is fine enough to get the hop pellets out of the brew.