my only 2 cents is basically to get 2 u locks (or at least get a cable. you want to secure the front wheel + frame to a bike rack or post. you also want another u lock or cable to secure the back wheel.
if you have a quick release saddle, carry that with you. if you don't make sure it has tight screws. thieves will steal even crappy saddles and it's a PITA to ride home with no saddle (i have used an empty water bottle in emergency situations).
costco also has cheap bikes for around $100 sometimes.