South on I5, turn East (left) onto the 2. Arrive in Leavenworth where you can pick up supplies like groceries. Just as you enter the town, turn right before the first gas station onto Icicle road. Go 8 Miles (13km) or until you see Eminem. There should be a camp site on the left. Climbing can be reached by walking or driving to other climbing spots.
You can camp in the Icicle Valley at Eight Mile campground. Eight Mile campground has clean well water, picnic tables, and fire pits as well as several outhouses and garbage bins. If that campground is full, there is bridge creek campground. The area has over 200 sites and it is off season, there should be no problems finding a place to pitch a tent. The cost will be in the range of $9-12 per car per night.
Camping in Vantage is free, parking is free, but you have to pay if you want to do both in the same spot (??? pay at the general store). Free is a type of camping that implies that there are zero services including a supply of water of any kind. There are toilets, which keeps things cleaner, which is nice.
If your car is filled with people and gear, it is best to buy your food in the US. I recommend going to a grocery store close to Leavenworth (there is a Safeway at the East end of town). There is a tiny grocery store in Vantage that will sell you baked beans for the price of filet mignon. Beer is much cheaper in the States than in Canada. Remember that the drinking age is 21 so plan to bring from Canada if you so choose. You are not allowed to bring fruit, vegetables and beef across the border. You probably can, but you will have to lie to the border guards if you don't want to throw it out.
Leavenworth is primarly a trad climbing destination with some sport, top rope and bouldering. There is no instruction provided so please plan accordingly. There is a number of multi-pitch climbs in the area including "Outer Space", a 5.9 classic (One of Tyler Lynn's favourites).
Vantage is columnar basalt, which means it is really cool rock to climb, but maybe a little loose. Most of the climbs are single pitch sport or trad. Top roping is not recommended because there is a lot of loose rock at the top of climbs. As usual, the people who bolt climbs have something against top ropers. A top roper must have kicked their dog or something.
What to bring
Bring American money and a passport. You will get hosed on the exchange rate if you try and use a debit card. Bring your climbing gear, camping gear (reasonably warm), and a guide book (at least a photo copy). Should talk around to share tents and stoves.