Ah, Indianapolis. Indianapolis and Marriott seem to have a pretty good thing going. So good, though, that it can be a little confusing to figure out which Marriott is where you want to be.
The Marriott you want: Indianapolis Downtown Marriott, 350 West Washington Street. This is the one closest to the Convention Center, next to the Westin, south of the Government Center.
The other Marriotts in downtown Indianapolis (but not the correct one):
Marriott Place (aka conglomeration of several Marriott hotels)
The JW Marriott (aka the big blue one): if you end up here, you are a block away from the actual Marriott you want. Head towards downtown (away from the river). On the other side of the Government Center Parking Garage will be the Indianapolis Downtown Marriott (where you want to be).
Courtyard Indianapolis Downtown: this is on the west (river) side of the JW, immediately next to the JW. One of two Courtyards in downtown Indy.
Fairfield Inn & Suites: next to the Courtyard above.
Springhill Suites: also in the Marriott Place.
Other two downtown Marriotts not mentioned yet (these are kind of back to back–they share their parking lot with each other):
Courtyard Indianapolis at the Capitol: the other Courtyard, in between New York & Vermont streets, about 3.5 blocks too far north.
Residence Inn Indianapolis Downtown along the Canal: this does face directly onto the canal; again, still 3.5 blocks north of where you should be.
I’ve included all of the names here so hopefully, if you end up at the wrong one, you will know either to head away from the river and towards downtown, or head south (towards Government buildings & parking garages). Good luck & see you soon!
Oh, another tip–highly recommend getting to the hotel from West Street (there are exits off of I-65 and I-70 for West Street); there are a lot of one-way streets downtown and construction. Maryland is one-way east; Washington is one-way west; Missouri runs in between then and is two-way.