He does have the Travelers yet either, they might not even be ziz bombs yet.
Ziz hit Madison, WI in December 2009, so they've been travelling and ticking for seven months at this point. Where are they? Not BB or Boston, that's all I know.
As for Coil (who has only been mentioned from Lisa's perspective), how Taylor's existence fouls his power depends on how willing his Shard is to model based on observed behavior, and whether it
A) looks to the future without simulating anything to predict which path he will choose and then simulates the other in real time,
B) simulates both paths to their conclusion immediately, then sets him on the path he chose while showing him the other, or
C) simulates both paths to their conclusion immediately, then puppets him to the end.
(Yes, simply viewing the future is a thing the Entities can do. Scion uses it to check (accurately!) and tune parts of the Cycle before they even reach the Milky Way. This does not alert him to Eden's death. Getting the data produced by the Cycle with future sight would be much more expensive than actually doing it, though.)
If it bothers to try modeling Taylor and lets Coil use his power, then option A) will feed him increasingly wrong results from the simulated timeline as it interacts with Taylor, meaning he gets bad intel. He is unlikely to notice it is bad intel as the real him has two-way real time interaction with the simulated him. This leads to making plans based on false information, which leads to plans failing. Possibly he tries to select the simulated timeline, which of course fails.
B) will see the simulated timeline diverging from truth even faster AND the thoughts and actions of the simulated Coil desyncing from the real Coil to the extent Taylor's actions affect the real Coil. He will notice, it will cause confusion and consternation. Even if he figures out the timeline he doesn't get to keep is bad intel and why, that still means his power is unreliable, which is possibly
worse (for him) than not having his power at all. He is likely to attempt to close the 'wrong' timeline and make his choice at the 'wrong' time; in both cases his Shard has to make a decision. To the extent Cauldron vial powers can make decisions.
C) means that Coil's Shard has to decide whether to end the simulation when puppet-Coil ends up in an unexpected situation. Does Coil suddenly find himself 'back in time' with only one timeline active, possibly a headache, and no idea what went wrong, or does puppet-Coil continue to act out increasingly nonsensical actions until he wakes up and has to deal with the consequences?
All of which assumes Coil's power tries to model Taylor (and Vicky, and probably Inari) instead of canceling the simulation as soon as it involves her.