Having trouble reading some charts (SBMG-SBLO)
Interesting academic exercise crimson_king. I don’t think you would get cleared for or use this SID/IAP combo. The airports are too close together. You are basically using your destination airport’s NavAid as the beginning/start of your departure. You will overfly the airport before you get to the VOR that starts the procedure. Then, you would have to backtrack out to the arc, using LON as your IAF.
The plate that you referenced is just an instruction on how to get to the start of your departure. There is probably a textual ODP to go with it. If you were in IMC, you would remain under radar vectors and ATC control the entire time. They would probably give you instructions like: Fly runway heading climb and maintain 5000 radar vectors direct D270L cleared the VOR Z Runway 13. This is of course abbreviated since you would have a switch of ATC from tower to approach.
Based on the information provided, For the purposes of simming, your best bet is to:

Take off from the runway of predominant wind.

Remain in the traffic pattern and climb over the airport.

Climb until you are at 5000 feet or more. The reason for this is that the only altitude information I see on the plate are the Minimum Sector Altitude and the Maximum Elevation Figures.

Fly direct to MG123 using RNAV/GPS.

Switch to VLOC/VOR mode

Fly direct to D270L.

Begin your IAP
A second option is to just fly direct to LON using your Nav radio by the shortest route possible. Use MG123 as a fly over reference point. Maintain full throttle at Vx until 5000 feet. Once you are within 12 miles DME of LON. Start your descent down to 4100 feet. Join the arc wherever you happen to enter.


Celia is not marked as an IF/IAF. So, I would avoid going directly there. It would be a perfectly good option if you were being radar vectored and cleared there by ATC.