Based on the table of Percentage Points of the Chi-Square Distribution. the threshold is 3.84 for the alpha of 0.05.  The chi-square score is 50.176 larger than the threshold value of 3.84. Thus, the null hypothesis is rejected.  
Conclusion
The results of the Chi-square test and z-test both indicate I can reject the null hypothesis. However, I believe the Chi-square will be relatively robust because it works for comparison of two proportions,  and z-test is work better with one sample and one distribution in order to see the goodness of fit between the observation and expectation.  However, I also see the weakness of this analysis is to separate the age group better between age between (18 - 35), Also I might think about to choose subscriber type to process further analysis in a way to adjust the inference from the activities by tourists or visitors. In order to build a robust analysis. We can feed more monthly data, so we can test our hypothesis with the time series analysis.
Github Link:
https://github.com/jianweili0/PUI2018_jl9200/blob/master/PUI2018_jl9200/HW8_jl9200/HW8_2_jl9200_miniproject_citibike-Copy.ipynb