I visited Guadalajara for a few days and it was great! People were extremely friendly and tolerant of my 100 word spanish vocabulary. Housing and living is very reasonable, food is quite cheap, the weather is mild and the city is lively, if a bit spread out. I didn't feel more unsafe than I did in Istanbul. I didn't get a chance to see the tech stuff but there were a bunch of companies and also a reasonably lively meetup scene too!