If you don't look at them before buying in person, you will get burned at some point and regret it.   

If you do decide to do mailer(s), then I would advise you to personalize the card and do a handwritten note. 

My wife and I have overhauled our personal budget to reflect the 'pay yourself first' approach (allocate in order: income comes in -> invest -> donate -> fixed expenses -> variable expenses -> fun $$).We are looking to see what experienced people generally recommend for a holding tank for that 'invest' allocation while we target our first real estate deal.What financial vehicles have you guys used that works well for this?

Conducted personal research.

They seem to be a reputable company, but nothing beats personal testimonies!

Definitely a personal preference.

Do you sell / buy real estate in Mexico personally? 

I will make that proposal to the person I am talking and see where it goes.

If not from the person in office, then definitely from the person running against them.

Try being an agent, your phone number is EVERYWHERE and you get targeted by a whole industry that wants to sell you the latest gimmick.Here is what helped me.I answer calls and when it's a telemarketer I will interrupt them and say very friendly (because I don't hate the poor person who gets paid to do this and coached to be ruthless): Hey, so glad you called, can you do me a big favor?