Wow! Where to start?
First of all, the topic here is about "border hopping" which refers to crossing a border into another country. Crossing a border or entering into another country is an action or activity with legal consequences. Therefore, before you speculate with endless nonsense, you should first consult with an immigration attorney about the intricacies of crossing a border, either into Panama or Nicaragua. On a related topic, the issue about drivers licenses is also a legal matter, so this should be consulted with an attorney as well.
The purpose of Expat.com is to somehow assist people to adjust when relocating to different countries. Relocation infers a notion of permanency, which is not compatible with the concept of tourism or tourist. For the most part, the post in this topic are relevant to people who are crossing the border with the intent to maintain the perpetual tourist status. So, these are my two cents on this topic, if you are relocating to any a country, in this case Costa Rica, you should obtain a long term immigration status (colloquially: visa) such as a permanent residence, temporary residence, special category, or stay.
The tourist visa is not designed, neither here nor in any other country, for people to remain for extended periods of time. So, if you are trying to use something for an unintended purpose, it is not going to work and you are going to run into problems. Especially now that the Immigration Department is making it more difficult for foreigners to function in Costa Rica as tourist. My advice, if you want to visit Costa Rica for a vacation, then use a tourist visa. On the other hand, if you want to relocate to Costa Rica, obtain a long term immigration status.
Now, regarding the 90 day visa: this available to foreign nationals from the first group of visa exempt countries, which are for the most part industrialized "rich" countries such as Canada, US, UK, France, Germany, Italy, Japan, you get it. Although, nationals from this countries are allowed to enter the country with only their passports it is required for them to provide proof of a return ticket to go back home. In the case of people flying into Costa Rica, this evidence is going to be required at the airport prior to boarding the plane to Costa Rica. In the case of people trying to enter by a border post, the Immigration Officer is going to require either a bus ticket back to bordering country, or a airplane ticket back to their home country.
Something that you need to take into consideration when crossing a border, is that you will go through two immigration post, one for each country. We have been noticing over the past few months, that the immigration officers from Panama are becoming very difficult and arbitrary. These are very simple people with no manners or social skills. You do not want to argue with them, you just need to comply, and as noted in this post, they will request $500USD in cash and a return ticket by bus to Costa Rica or air plane ticket to your home country.
In the Nicaraguan border, they are a just happy to let you in.
Regarding border crossings when you have an application pending or already have residence. If you have already filed an application for some sort of immigration status in Costa Rica, it is not required for you to leave the country every 90 days. The same applies if you have already obtained your status. Please keep in mind that this is only applicable from an immigration perspective.
Regarding the Drivers License:
this is what the transit law says about licenses:
Section 84. Requirements for a license for the first time.
In order to obtain a license, a person will need to comply with the following requirements:
a. Be of legal age
b. Be able to read and write
c. Provide a Medical Examination
d. Complete the driving test
e. Complete the written test
Section 91. Validation of Licenses for Foreigners
a. A foreign national with a foreign driver's license and with a tourist visa is allowed to use that same driver's license for a period of three months.
b. Foreign nationals who have remained in the country for a continued period of more than three months, can validate the foreign driver's as long as he/she complies with all above requirements with the exception of the driving test and the written test in addition to providing a document from the immigration department indicating their legal status in the country.
To summarize,
1. If you have a valid passport, valid 90 day visa, and a valid driver's license, you can drive in Costa Rica without the risk of getting ticket.
2. If you have a valid passport, you can go ahead and obtain the drivers license for which you will need to comply with requirements in section 84.
3. If you do not want to do the tests you can validate your foreign driver's license if you have a valid passport, 90 visa and driver's license, provided that you provide a document from the Immigration Department indicating your status in Costa Rica.
Regarding immigration regulations, once your application is filed, you are not required to leave the country any more in order to obtain a 90 day visa. The immigration laws allows you to remain in the country while the application is pending. But immigration regulations are different from transit regulations. So, although you are allowed to stay in the country while the application is pending, a transit officer will give you a ticket of you have overstayed the 90 days.
I hope this information helps to clarify all of the misinformation being circulated around. Once again, I suggest contacting an attorney to assist you with legal matters. You can refer to the list of attorneys provide by the US consulate or the consulate from the country you are from.