Placing the rebar and grouting the cells is not random. There are several issues to consider for a structurally sound installation: 1) size, spacing and grade of rebar, 2) type of grout, 3) lap of rebar splices.
1) I too live in a seismically active area and for an 8” wide wall about 8’-10’ high we use #5 rebar at 24” on center each way. Place one bar vertically in each corner plus one on each side of each door and window opening plus one horizontally in the very bottom and very top cell. I’d use two horizontal bars minimum over 4’ openings and smaller. (The amount of rebar depends on height, load, etc. You’ll want to contact an architect or structural engineer to calculate loads.)
Rebar is meant to be on the tension side of the wall with adequate space (about 1”) around it for grout to flow and bond to it.
2) What you put in the hollow cells is called “grout”, not cement or mortar. Grout comes in “fine” and “course”. You’ll probably want “fine”, because it will flow better around rebar, etc. Grout is very liquidity and flows like tomato soup. Make sure the slump is between 8” and 10” so it will flow everywhere and bond to the rebar. (If it’s too stiff or if you use cement or mortar it will not bond properly and the rebar will be useless.
3) Rebar is in tension, so you’ll need to lap splices a minimum of 30 bar diameters. So, for a 5/8” rebar, you’ll need to lap them about 19”-20” minimum. Also, make sure the rebar coming out of the foundation is on the same spacing as your vertical bars so they can be lapped. (Make sure the bars out of the foundation is where you want the bars in the hollow blocks.) Also, make sure the rebars extend 30 bar diameter around all corners.
Someone mentioned holding each horizontal course of grout down a few inches to help with strength and prevent water leaks. Don’t do that. If water leaks in it will settle in the cavity and create mold. Keep each course of grout level so if there is a leak it can dry out through the sand crack.
Someone mentioned installing the grout in the horizontal cells first. This can’t happen because grout is very liquidity and will flow from cell to cell seeking its own level.
Laying concrete block is tricky and takes some skill. I’d get someone with experience to help/guide.