Laughing off safety advice as "common sense" that "everyone has" is not helpful to those going alone in an unfamiliar city. Even if events are 99% safe, bad things happen.
Please do not belittle the safety precautions that we need to take.
Despite all the wonderful folks you will meet at a Con, it is still uncomfortable being a woman alone. Join the newbie groups and specifically look up some geek girl groups.
Other women had great advice: leave early, stay with crowds, avoid street folks, and don't drink much your first year. As a younger woman who may be cosplaying in an attractive costume, here's what you need to know:
Do not depend on technology to help you.
You will not have a good signal in a convention area and if you finally get a message, your battery will most likely die. Print out a map and ask for directions from a staff member before venturing out somewhere.
Be careful where you park.
The night time trek back to your car is way sketchier than it was Saturday morning. Although rare, there are parking scams and other petty crimes that happen during a busy weekend. Don't believe what someone on the street tells you. Look for authentic business sign information before you ever hand over money.
Be prepared to deal with uncomfortable attention and sexual harassment.
Are you willing to cause a scene to defend yourself or are you the deer in headlights type? I know plenty of strong women who never expected to be victims. Having a plan can help you have a good con experience.
Diffuse the situation by having some funny lines to let men down gently.
Rebuke a heckler in character or call out to someone nearby to join you on a quest.
A change in topic or bringing another person into the conversation can shift the tone.
I would love to say that staff members are always around and can help you, but unfortunately this isn't the case. What works best for me is using a teacher/mom voice to politely tell the offender that their behavior is inappropriate and that they are making you uncomfortable. Saying this simply and loudly has been enough to embarrass the offender and sometimes merits an apology.
It may seem like "common sense" but in the moment, instincts can leave you. Having a backup plan and preparing a response can genuinely help de-escalate a potentially negative situation.