How can I get informed if a titled chess player will be holding a simul? I would like to go to more simuls, but I'm unsure when they're held and at what location. How can I get informed of such information?
Generally, you should belong to a club if you wish to play titled players in simuls. The more active your club is the more likely the club is able to do, which includes paying titled players to host simuls. 

Other than that, you could consider hosting the event. Simply contact titled players on sites like chess.com and the ICC to see if they're interested. They'll usually charge a fee, and off you go. 

Sometimes titled players host simuls at tournaments as well, so it would do you well to find out what tournaments are near you or that you can attend. If you're in the US, then both USCF and FIDE are good for finding upcoming tournaments. Outside the US and you'll want to stick to FIDE as well as other national federations to find chartered/sponsored tournaments.