Probably they just gave you 20-50 oil instead of whatever thinner oil you've been using...but that's just a guess.
Conventional KLR wisdom for pre-2008 says you fill to the top of the window for a level, balanced bike (which is above the top mark on the sight glass). I don't know about 2008+. Overfilling is no good. Underfilling is no good. Note however that you need to run the bike briefly to soak the new filter and so on before judging whether it's over-full or not. Personally, I stick around and talk to the guys doing service on my bike: it's too easy for them to leave out an o-ring, strip a bolt using old channel-lock pliers, throw away the little piece that fits inside the oil filter or in other respects mess things up.
You're in Mexico, right? You can change your own oil and bring used oil into any oilchange place. Be nice to them. They'll take your used oil. Sometimes if you ask they'll let you use their pan and service bay to do the change. It's not America, and no one is worried about the details; they're more concerned about whether you're a nice guy. Good practice (being a nice guy, I mean).
I never heard what was wrong with your bike back in California. Was it really the coil or the stator or whatever you suspected?