You're fine if you're driving or taking Ubers, there are areas where crime might be heavier but overall it's a nice place. Not to roam around at night... Also my advice is to make group plans, that is the safest way.

Like any other place, Alajuela is full of tourists and locals and good and malicious people. It is better to be cautious and never leave things unattended. At night or during the day, avoid taking out your cell phone or cash; try to be as cautious as possible.