This is interesting.
Just had a look how some popular dictionaries define the word touristy and it
appears the word does have negative connotations: (at least to the compilers of
the dictionaries).
    - According to Cambridge Dictionary A touristy place is not attractive because a lot of tourists visit it and it is full of things for them to buy and do
 
    - The Oxford Dictionary declares the term as being an informal word defines it as follows: Relating to, appealing to, or visited by tourists (often used to suggest tawdriness or lack of authenticity)
 
    - Collins Dictionary goes even further :
    If you describe a place as touristy, you do not like it because it is full of tourists or full of things for tourists to buy and do.
    [informal , disapproval]
    Visit some of the less touristy islands.
  and then gives an "American usage"
  touristy in American English(ˈtʊrɪsti ; toorˈistē)
  adjective
  of or for tourists
  often used with mild contempt to suggest banality or tastelessness
 
    - and the Longman dictionary, to conclude with:
    Related topics: Tourism
  tour‧ist‧y /ˈtʊərəsti $ ˈtʊr-/ adjective informal
  1 a place that is touristy is full of tourists and the things that attract tourists – used to show disapproval
  Benidorm is too touristy for me.
  2 a touristy activity is typical of the things that tourists do – used to show disapproval
  We did all the usual touristy things
 
It should be noted, however, that other online dictionaries give a much more "neutral" meaning :  
 
 
Dictionary.com  -  
pertaining to or characteristic of 
tourists:
a touristy attitude.
2.appealing to or frequented by 
tourists:
a touristy restaurant near the Eiffel Tower.