To avoid Suna Seni early on, I believe that Sikret has said going from the Promendade to the Slums to the Government district to the City Gates to Umar Hills is a safe route. (I hope I got that right.) Well, going from from the Government District to the Temple District (for Keldorn) instead of to the City Gates triggers the encounter. I groaned when I saw the dreaded sphere on the enemy mage, and immediately reloaded to check to see if this was a random encounter that may not be there if I tried again. No luck. However, I did manage to chop them up this time when I fought without too much trouble. Wooot, I'm learning to play IA! If this is an indication, I expect my second run through to take many less reloads. Hurah!
Nevertheless, I suggest delaying the encounter with Suna Seni to *at least* 3-7 (random) game days. I can imagine that some newcomers to the game would be very turned off by this encounter on Day 1! I know that I wasn't very fond of it on my first run.
I would have put up a spoiler warning, but if you don't know who Suna Seni is, I suppose that you are not spoiled.